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

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("YES")
#define p_no() p("NO")

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    double X, Y, N;
    cin >> X >> Y >> N;

    vector<ll> A(N);
    FOR(i, 0, N){
        cin >> A.at(i);
    }

    FOR(i, 0, N-1){
        double koba = A[i];
        double sisho = Y * A[i] / X;

        if(sisho > A[i+1]){
            p_no();
            return 0;
        }
    }
    p_yes();
    
    return 0;
}