#include<iostream>
using namespace std;

int main()
{
	int n,s;
	cout<<"n=";
	cin>>n;
	while(n>9)
	{
		s=0;
		while(n>0)
		{
			s=s+n%10;
			n=n/10;
		}
		n=s;
	}
	cout<<n;
}