#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)


int X, Y, N, A[101];
//-----------------------------------------------------------------
#define EPS 1e-10
string sol() {
    rep(i, 0, N - 1) {
        int x = A[i], y = A[i + 1];
        double tx = 1.0 * x / (X * 1000);
        double ty = 1.0 * y / (Y * 1000);

        if (ty < tx - EPS) return "NO";
    }

    return "YES";
}
//-----------------------------------------------------------------
int main() {
    cin >> X >> Y >> N;
    rep(i, 0, N) cin >> A[i];

    cout << sol() << endl;
}