#include<bits/stdc++.h>
using namespace std;
char a[120];
int c=0;
//
int x; int main(){
    gets(a);
    for(int i=0;i<strlen(a);i++){
         c=c+(a[i]-'0');
    }
    cout<<c;
    return 0;
}
/**************************************************************
	Problem: 1115
	User: wangyousi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/