#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define endl "\n"
#define rep(i, a, n) for (int i = a; i < n; ++i)

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    int ans = n % 9;
    if (ans == 0) ans = 9;
    cout << ans << endl;
    return 0;
}