#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
#include<sstream>
#include<iterator>
#include<list>

using namespace std;

typedef  long long int lint;

#define rep(i, n) for (lint i = 0; i < n; i++)
#define sort(v) sort((v).begin(), (v).end())
#define reverse(v) reverse((v).begin(), (v).end())
#define upper(v,hoge) upper_bound(v.begin(),v.end(),hoge)
#define lower(v,hoge) lower_bound(v.begin(),v.end(),hoge)
#define mp make_pair
#define enld endl

lint sumrank(lint n) {
	//各位の和を返す
	string s = to_string(n);
	lint ret = 0;
	for (int i = 0; i < s.size(); i++)ret += (s[i] - '0');
	return ret;
}

int main() {
	lint N;
	cin >> N;
	rep(i, 100) {
		N = sumrank(N);
	}
	cout << N << enld;
}