#include <bits/stdc++.h>
#ifdef _DEBUG
#include "debug.hpp"
#else
#define debug(...)
#endif
#define fastIO (cin.tie(0), cout.tie(0), ios::sync_with_stdio(false))
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define precise(i) fixed << setprecision(i)
using ll = int64_t;
using ul = uint64_t;
using namespace std;

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

void solve() {
  int n;
  cin >> n;
  while (n > 10) {
    n = sumDigit(n);
    debug(n);
  }
  cout << n << endl;
}

void wrapper() {
  rep(i, 2) {
    cout << "[TEST " << i << "]\n";
    solve();
    cout << "\n";
  }
}

int main() {
  fastIO;
#ifdef _DEBUG
  wrapper();
#else
  solve();
#endif
}