#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

int calc(int n) {
    int res = 0;
    while (n > 0) {
        res += n % 10;
        n /= 10;
    }
    return res;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;
    for (int i = 1; i < 100; i++) {
        n = calc(n);
    }
    cout << n << newl;

    return 0;
}