#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll=vector<long long>;
template<typename T>
T get(){T r;cin>>r;return r;}

int main() {
    string n=get<string>();
    ll cnt=0;
    for(int i=1;i!=n.size();i++){
        if(n[i]=='3'){
            cnt++;
        }
        else{
            cnt=-1;
            break;
        }
    }
    cout<<cnt<<endl;

    system("pause");
}