#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
//#define int long long
using namespace std;
typedef long long ll;
const int INF = 1e9;



signed main()
{
    int X, Y;
    int N;
    int A[85];

    cin >> X >> Y;
    X *= 1000; Y *= 1000;
    cin >> N;
    REP(i,N) cin >> A[i];

    double t1[85], t2[85];
    REP(i,N) {
        t1[i] = (double)A[i] / X;
        t2[i] = (double)A[i] / Y;
    }

    REP(i,N-1) {
        if (t2[i+1] < t1[i]) {
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
}