#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define rep_lr(i,l,r) for(int i=(l);i<(r);i++)
#define all(x) (x).begin(),(x).end()
#define V vector
typedef V<int> vi;
typedef V<vi> vvi;
typedef long long ll;
typedef pair<ll, ll> P;
typedef tuple<int, int, int> T;
constexpr int INF = INT_MAX >> 1;
constexpr ll LINF = 5000000000000000LL;
constexpr int MOD = 1000000007;

int ten(int i) {
	int ret = 0;
	while (i) {
		ret += i % 10;
		i /= 10;
	}
	return ret;
}


int main() {
	
	int n;
	cin >> n;
	rep(i, 99) {
		n = ten(n);
	}

	cout << n << endl;
}