#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

int main() {
    string s;
    cin >> s;

    int cnt = 0;
    for (int i = 1; i < s.size(); ++i) {
        if(s[i]!='3'){
            cout << -1 << endl;
            return 0;
        }
        else
            ++cnt;
    }

    cout << cnt << endl;

    return 0;
}