// No.512 魔法少女の追いかけっこ
// https://yukicoder.me/problems/no/512
//

#include <iostream>
#include <vector>
#include <string>
using namespace std;

string solve(double X, double Y, vector<int> &corners);


int main() {
    double X, Y;
    cin >> X >> Y;
    int N;
    cin >> N;
    vector<int> corners(N);
    for (auto i = 0; i < N; ++i)
        cin >> corners[i];

    string ans = solve(X, Y, corners);
    cout << ans << endl;
}

string solve(double X, double Y, vector<int> &corners) {
    for (auto i = 1; i < corners.size(); ++i) {
        if (corners[i-1] / X > corners[i] / Y)
            return "NO";
    }
    return "YES";
}