#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using ll =  long long ;
using P = pair<int,int> ;
const int INF = 1e9;
const int MOD = 1000000007;

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