#include <bits/stdc++.h>
#define rep(i, n) for (ll i = 0; i < n; ++i)
typedef long long ll;
using namespace std;
const int INF = 1e9;

int sumd(int x) {
    int res = 0;
    while (x != 0) {
        res += x % 10;
        x /= 10;
    }
    return res;
}

int main() {
    int n;
    cin >> n;

    rep(i, 99) {
        n = sumd(n);
    }
    cout << n << endl;

    return 0;
}