#include <iostream>
#include <utility>
#include <vector>
#include <string>
#include <cstdio>
#include <cmath>


using namespace std;

int main(){

    string n;
    long long int ans;

    cin>>n;

    for (int i=0;i<100;i++){
            ans=0;
        for (int j=0;j<n.size();j++){
            ans+=n[j]-'0';

           
        }
         n=to_string(ans);
            
    }
    cout<<ans<<endl;
    
    

   
    
}