# coding: utf-8
import array, bisect, collections, copy, heapq, itertools, math, random, re, string, sys, time
sys.setrecursionlimit(10 ** 7)
INF = 10 ** 20
MOD = 10 ** 9 + 7


def II(): return int(input())
def ILI(): return list(map(int, input().split()))
def IAI(LINE): return [ILI() for __ in range(LINE)]
def IDI(): return {key: value for key, value in ILI()}


def solve(X, Y, N, A):
    # x_m = X * 1000 / 3600
    # y_m = Y * 1000 / 3600
    l_x = [a / X for a in A]
    l_y = [a / Y for a in A]

    ans = "NO"
    for i in range(N - 2):
        if l_y[i + 1] < l_x[i]:
            break
    else:
        ans = "YES"

    return ans


def main():
    X, Y = ILI()
    N = II()
    A = ILI()
    print(solve(X, Y, N, A))


if __name__ == "__main__":
    main()