#include<iostream>

using namespace std;

string N;
int main () {
    cin >> N;
    if( N[0] != '1' || N[1] != '3' ) {
        cout << -1 << endl;
        return 0;
    }
    int ans = 0;
    for(int i=1; i<N.size(); i++) {
        if( N[i] == '3') ans++;
        else {
            cout << -1 << endl;
            return 0;
        }
    }
    cout << ans << endl;
    return 0;
}