#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    string S;
    cin >> S;
    if(S.size() == 1 || S[0] != '1'){
        cout << -1 << endl;
        return 0;
    }
    rep(i,0,S.size())if(S[i] != '3'){
        cout << "-1" << endl;
        return 0;
    }
    cout << S.size() - 1 << endl;
}