// you can also use imports, for example:
// import java.util.*;

// you can write to stdout for debugging purposes, e.g.
// System.out.println("this is a debug message");

class Solution {
    public int solution(int[] A) {
        // write your code in Java SE 8
    }
}

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    pass

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    pass

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    pass

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    pass

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    # write your code in Python 3.6
    pass

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_set = {}
    for 

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_list = {}
    for 

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for 

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for f

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        check_dict[i] = True

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_check_dict.get(i, False)
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if not is_unpaired:
            
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if not is_unpaired:
            check_dict[i] = True
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if not is_unpaired:
            check_dict[i] = True
        else:
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if not is_unpaired:
            check_dict[i] = True
        else:
            del 
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if not is_unpaired:
            check_dict[i] = True
        else:
            del check_dict[i]
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return check_dict.keys()[0]
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return list(check_dict.keys()[0]
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return list(check_dict.keys())[0]
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return list(check_dict.keys())[0]
            
        
        

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")

def solution(A):
    check_dict = {}
    for i in A:
        is_unpaired = check_dict.get(i, False)
        if is_unpaired:
            del check_dict[i]
        else:
             check_dict[i] = True
             
    return list(check_dict.keys())[0]