#include<stdio.h>
int main()
{
  long int n=0;
    int b;
    int sum=0;;
    scanf("%ld",&n);
    for(;n!=0;)
    {
        b=n%10;
        n=n/10;  //为0时候不进入循环
        sum+=b;
        
   }
    printf("%ld",sum);
    
}