#include <iostream>
#include <vector>
#include <algorithm>
#include <stdio.h>

using namespace std;

typedef long long ll;

template < typename T > T gcd (T a , T b) { if (a < b) swap(a , b); if (a % b == 0) return b; else return gcd (b , a % b); }
template < typename T > T lcm (T a , T b) { return (a / gcd (a , b) * b); }

int main () {
    ll x , y;
    cin >> x >> y;
    ll lc = lcm(x , y);
    int n;
    cin >> n;
    vector<ll> a(n + 1);
    for (int i = 1; i <= n; i++) {
       cin >> a[i];
       a[i] *= lc;
    }
    ll pos = 0;
    for (int i = 1; i < n; i++) {
        pos += (a[i] - a[i - 1]) * y / x;
        if (pos > a[i + 1]) {
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
    return 0;
}