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

template<class T> void vin(vector<T>& v, int n) {
    v.resize(n);
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
    }
}

int main()
{
    string s;
    cin >> s;

    bool ok = true;
    if (s[0] != '1')
    {
        ok = false;
    }

    for (int i = 1; i < s.size(); ++i) {
        if (s[i] != '3') {
            ok = false;
            break;
        }
    }

    if (ok) cout << s.size()-1 << endl;
    else cout << -1 << endl;

    return 0;
}