#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int X, Y, N;
    while (cin >> X >> Y >> N) {
        vi A(N);
        rep(i, N)cin >> A[i];
        int p = 0, q = 0;
        // X < Y

        bool ok = true;
        rep(i, N - 1) {
            int x = A[i] * Y, y = A[i + 1] * X;
            if (x > y) {
                ok = false;
                break;
            }
        }
        cout << (ok ? "YES" : "NO") << endl;
    }
}