#include <bits/stdc++.h>
#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
int main()
{
    string s;
    cin >> s;
    if (s[0] != '1')
    {
        cout << -1 << endl;
        return 0;
    }
    int ans = 0;
    for (int i = 1; i < s.size(); i++)
    {
        if (s[i] != '3')
        {
            cout << -1 << endl;
            return 0;
        }
        ans++;
    }
    if (ans == 0)
        ans = -1;
    cout << ans << endl;
    return 0;
}