#include <bits/stdc++.h>
using namespace std;

int main(){
    long long n, ans = 0;
    cin >> n;
    while(n >= 10){
        if(n % 10 == 3){
            ans++;
            n /= 10;
        }else{
            ans = 0;
            break;
        }
    }
    if(ans > 0 && n == 1) cout << ans << endl;
    else cout << -1 << endl;
}