Polycarpus adores TV series. Right now he is ready to finish watching a season of a popular sitcom "Graph Theory". In total, the season has *n* episodes, numbered with integers from 1 to *n*.

Polycarpus watches episodes not one by one but in a random order. He has already watched all the episodes except for one. Which episode has Polycaprus forgotten to watch?
The first line of the input contains integer *n* (2 ≤ *n* ≤ 100000) — the number of episodes in a season. Assume that the episodes are numbered by integers from 1 to *n*.

The second line contains *n* - 1 integer *a*<sub class="lower-index">1</sub>, *a*<sub class="lower-index">2</sub>, ..., *a*<sub class="lower-index">*n*</sub> (1 ≤ *a*<sub class="lower-index">*i*</sub> ≤ *n*) — the numbers of episodes that Polycarpus has watched. All values of *a*<sub class="lower-index">*i*</sub> are distinct.
#include <bits/stdc++.h>

using namespace std;

void solve() {
    int n;
    cin >> n;

    vector<int> arr = {};
    int val;

    for (int i = 0; i < n - 1; ++i) {
        cin >> val;
        arr.push_back(val);
    }

    sort(arr.begin(), arr.end());
    if (arr[n - 1] != n) {
        cout << n;
        return;
    }
    for (int i = 1; i <= n; ++i) {
        if (i != arr[i - 1]) {
            cout << arr[i - 1] - 1;
            return;
        }
    }
}

int main(int argc, char* argv[]) {
    ios::sync_with_stdio(false);
    cin.tie(0);

    solve();

    return 0;
}