#include <algorithm> #include <cmath> #include <cstdint> #include <cstdio> #include <iomanip> #include <iostream> #include <map> #include <queue> #include <set> #include <stack> #include <string> #include <vector> using namespace std; #define rep(i, n) for(int(i) = 0; (i) < (n); (i)++) #define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++) #define All(v) (v).begin(), (v).end() #define pb push_back #define MP(a, b) make_pair((a), (b)) using ll = long long; using pii = pair<int, int>; using pll = pair<ll, ll>; const int INF = 1 << 30; const ll LINF = 1LL << 60; const int MOD = 1e9 + 7; ll digsum(ll a) { ll ret = 0; while(a > 0) { ret += a % 10; a /= 10; } return ret; } int main() { ll N; cin >> N; rep(i, 100) { N = digsum(N); } cout << N << endl; return 0; }