#The Biggest Water Problem#

#include <stdio.h>
int UnitSum(int x)
{
    int sum = 0;
    while (x)
    {
        sum += x % 10;
        x /= 10;
    }

    return sum;
}


int main() {
    int num = 0;
    while (scanf("%d",&num) != EOF) 
    { 
        while (num > 9)
        {
            num = UnitSum(num);
        }

        printf("%d ",num);
    }
    return 0;
}