#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;

int calculateDigitSum(int n) {
    int sum = 0;
    while (n != 0) {
        sum += n % 10;
        n = n / 10;
    }
    return sum;
}

int main() {

    int N;
    cin >> N;

    for (int i = 1; i <= 100; ++i) {
        N = calculateDigitSum(N);
    }

    cout << N << endl;


    return 0;
}