#include <iostream>

int main() {
    int n;
    std::cin >> n;

    int sum = 0;
    for (int i = 0; i < n; i++) {
        int a;
        std::cin >> a;
        sum += a;
    }

    int n_sum = n * (1 + n) / 2;
    int result = (n_sum - sum) >= 0 ? n_sum - sum : sum - n_sum;
    std::cout << result << std::endl;
}