// 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)
    const len = A.length;
    let total = ((len + 2) * (len + 1)) / 2;

    for (const a of A) {
        total -= a;
    }
    return total;
}

// 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)
    const len = A.length;
    let total = ((len + 2) * (len + 1)) / 2;

    for (const a of A) {
        total -= a;
    }
    return total;
}

// 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)
    const len = A.length;
    let total = ((len + 2) * (len + 1)) / 2;

    for (const a of A) {
        total -= a;
    }
    return total;
}

// 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)
    const len = A.length;
    let total = ((len + 2) * (len + 1)) / 2;

    for (const a of A) {
        total -= a;
    }
    return total;
}

// 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)
    const len = A.length;
    let total = ((len + 2) * (len + 1)) / 2;

    for (const a of A) {
        total -= a;
    }
    return total;
}