#include <algorithm>
#include <array>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

int main() {
    int32_t n;
    cin >> n;
    int32_t sum = 0;
    for (auto i = 0; i < n; ++i) {
        int32_t a;
        cin >> a;
        sum += a;
    }
    cout << abs(sum - n * (n + 1) / 2) << endl;
    return 0;
}