#include <iostream>
#include <stdio.h>
using namespace std;
int main() {
// your code goes here
char cs[1001];
while(1){
scanf("%s",cs);
if(cs[0]=='0'&&cs[1]=='\0')break;
int ans=0;
for(int i=0;cs[i]!='\0';i++){
ans+=cs[i]-'0';
}
printf("%d\n",ans);
}
return 0;
}
