#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;

#define ll         long long
#define PI         acos(-1.0)
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)

int main(){
    double X, Y;
    cin >> X >> Y;
    int N;
    cin >> N;
    double a, b;
    FOR(i,0,N){
        double in;
        cin >> in;
        if(i==N-2) a = in;
        if(i==N-1) b = in;
    }
    if(a/X*Y<=b){
        cout << "YES" << endl;
    }
    else cout << "NO" << endl;
    return 0;
}