#include<iostream>
using namespace std;

int main () {
    float X, Y;
    cin >> X >> Y;
    float x, y;
    x = X * 1000 / 3600;
    y = Y * 1000 / 3600;
    int N;
    cin >> N;
    int A[81];
    for (int i = 0; i < N; i++) {
        cin >> A[i];
    }
    for (int i = 0; i < N - 1; i++) {
        if ((A[i] * y / x) > A[i + 1]) {
            cout << "NO" << endl;
            goto label;
        }
    }
    cout << "YES" << endl;
label:
    return 0;
}