// Template
#include <bits/stdc++.h>
#define rep_override(x, y, z, name, ...) name
#define rep2(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, r) for (int i = (l); i < (r); ++i)
#define rep(...) rep_override(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003;
template <typename T> inline bool chmin(T& x, const T& y) {if (x > y) {x = y; return 1;} return 0;}
template <typename T> inline bool chmax(T& x, const T& y) {if (x < y) {x = y; return 1;} return 0;}
struct IOSET {IOSET() {cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10);}} ioset;

// Main
int main() {
    int n;
    cin >> n;
    vector<int> a(100, 0);
    a[0] = n;
    rep(i, 1, 100) {
        while (a[i - 1]) {
            a[i] += a[i - 1] % 10;
            a[i - 1] /= 10;
        }
    }
    cout << a[99] << "\n";
    return 0;
}