#include <iostream>
#include <cassert>
using namespace std;

inline static constexpr int digit_sum(int N, int K) {
    int sum = 0;
    for (; N > 0; N /= K) sum += N % K;
    return sum;
}

int main() {
    int N;
    cin >> N;
    assert(1 <= N && N <= 1'000'000'000);
    for(int i = 2; i <= 100; ++i) {
        N = digit_sum(N,10);
    }
    cout << N << endl;
    return 0;
}