// Missing a space
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<(int)(n); ++i)
using namespace std;
using ll = long long;
using ull = unsigned long long;

int main(){
    int C;
    cin >> C;
    int cnt = 0;
    while(C>9){
        int cur = C%10;
        if(cur != 0) ++cnt;
        C /= 10;
    }
    cout << cnt << endl;
    return 0;
}