#include <bits/stdc++.h>
#include <string.h>
#define rep(i,n) for(int i = 0; i < n; i++)
#define srep(i,a,b) for(int i = a; i < b; i++)
#define all(A) (A).begin(),A.end()
#define MOD 1000000007
using namespace std;
using ll = long long;
using P = pair<int,int>;
using Graph = vector<vector<int>>;

int main(void){
	string s; cin >> s;
	string t = "1";
	rep(i,100){
		t += "3";
		if(s == t){
			cout << i+1;
			return 0;
		}
	}
	cout << -1;
}