#include <bits/stdc++.h>
using namespace std;
//型に気を付けよう
//a=0x61=97 '0'=0x30=48
#define rep(i,n) for(int i=0;i<n;i++)
typedef long long  ll;
typedef long double  ld;
typedef string str;
typedef pair<int,int> pairii;
typedef vector<int> veci;
const double pi=3.1415926535;
const ll  mod=1000000007;
//桁数指定　cout << fixed << setprecision(2)
int sum(ll n){
    int sum=0;
    for(int i=9;i>=0;i--){
        ll x=n/(pow(10,i));
        sum+=x;
        n-=x*pow(10,i);
    }
    return sum;
}
int main() {
    ll n;
    cin>>n;
    rep(i,100){
        n=sum(n);
    }
    cout<<n<<endl;
}