#include <iostream>
#include <string>
using namespace std;
int main(){
	string N;
	cin >> N;
	int ans = N.size() - 1;
	bool ok = true;
	if (N[0] != '1'){
		ok = false;
	}
	for (int i = 0; i < ans; i++){
		if (N[i + 1] != '3'){
			ok = false;
		}
	}
	if (ans == 0){
		ok = false;
	}
	if (!ok){
		cout << -1 << endl;
	} else {
		cout << ans << endl;
	}
}