#include <iostream>
#include <sstream>

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string token;
    float coord[2];

    for (int i = 0; getline(cin, token, ','); i++) {
        coord[i] = stof(token);
    }

    if (-1 <= coord[0] && coord[0] <= 1 && -1 <= coord[1] && coord[1] <= 1) {
        cout << "yes" << endl;
    } else {
        cout << "no" << endl;
    }

    return 0;
}