#include <bits/stdc++.h>
using namespace std;

int main(){
    int Vx, Vy, tmp, N, i;
    vector <int> kyori;

    cin >> Vx >> Vy >> N;
    while(cin >> tmp){
        kyori.push_back(tmp);
    }

    for(i = 0; i < N - 1; i++){
        if(Vy*kyori[i] > kyori[i + 1]*Vx){
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
    return 0;
}