#include "bits/stdc++.h"

using namespace std;

typedef pair<int, int> P;
#define int long long
#define ll long long
#define mod 1000000007
#define INF (1LL<<60)

#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)


signed main(){

	string s;
	cin >> s;

	if (s[0] != '1'){
		cout << -1 << endl;
		return 0;
	}
	if (s.length() == 1){
		cout << -1 << endl;
		return 0;
	}

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

	return 0;
}