// 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.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    for(int i = 0; i < )
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    for(int i = 0; i < A.leng)
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 
    for(int i = 0; i < A.length; ++i) {

    }
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number = number ^ (i + 1) ^ A[i];
    }

    return number;
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number ^ (i + 1) ^ A[i];
    }

    return number;
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number ^= (i + 1) ^ A[i];
    }

    return number ^ A.length + 1;
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number ^= (i + 1) ^ A[i];
    }

    return number ^ (A.length + 1);
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number ^= (i + 1) ^ A[i];
    }

    return number ^ (A.length + 1);
}

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)

    let number = 0;
    for(let i = 0; i < A.length; ++i) {
        number ^= (i + 1) ^ A[i];
    }

    return number ^ (A.length + 1);
}