#include <stdio.h>

int main() 
{   
    int n = 0;
    scanf("%d",&n);
    int i =0;
    int j = 0;
    for(i=4;i>0;i--)
    {
        j = j +n%10;
        n /= 10; 
    }
    printf("%d",j);
    return 0;
}