include<bits/stdc++.h>

using namespace std;
int work(int n)
{
if(n<10)
return n;
else{
int t=0;
while(n>0){
t+=n%10;
n=n/10;
}
return work(t);
}
}
int main()
{
int n;
cin>>n;
cout<<A(n);
}