#include <iostream>
using namespace std;
int main() {
    int n; cin >> n;
    for (int i = 0; i < 99; ++i) {
        int c = 0;
        c += n / 1000000000; n = n % 1000000000;
        c += n / 100000000; n = n % 100000000;
        c += n / 10000000; n = n % 10000000;
        c += n / 1000000; n = n % 1000000;
        c += n / 100000; n = n % 100000;
        c += n / 10000; n = n % 10000;
        c += n / 1000; n = n % 1000;
        c += n / 100; n = n % 100;
        c += n / 10; n = n % 10;
        c += n;

        n = c;
    }
    cout << n << endl;
}