#include<iostream>

#include<cstdio>

#include<algorithm>

#include<string>

#include<cstring>

#define ll long long

using namespace std;

#define maxn 1000000000

char s[maxn];

int main()

{

    while(~scanf("%s",s))

    {

        if(s[]=='')

            break;

        ll sum=;

        ll len=strlen(s);

        //(1)

        for(int i=; i<len; i++)

        {

            sum+=s[i]-'';

        }

        ll tmp=sum;

        while(sum>=)

        {

            sum=;

            while(tmp)

            {

                sum+=tmp%;

                tmp/=;

            }

            tmp=sum;

        }

        cout<<sum<<endl;

    }

    return ;

}