#include <bits/stdc++.h>
using namespace std;
int main() {
    string S; cin >> S;
    if (S.size() == 1 && S.at(0) == '1')cout << -1 << endl;
    else if (S.at(S.size() - 1) == '1' || S.at(S.size() - 1) == '3'||S.at(S.size() - 1) == '5' || S.at(S.size() - 1) == '7' || S.at(S.size() - 1) == '9')cout << 1 << endl;
    else cout << -1 << endl;
}