package main

import (
	"fmt"
)

func main() {
	var X, Y float64
	fmt.Scan(&X, &Y)
	x := X * 60 * 60 / 1000
	y := Y * 60 * 60 / 1000
	var N int
	fmt.Scan(&N)
	A := make([]float64, N)
	var a float64
	ans := "YES"
	for i := 0; i < N; i++ {
		fmt.Scan(&a)
		A[i] = a * 1000
		if i > 0 {
			d := A[i] - A[i-1]
			t := A[i] / y
			dy := A[i]
			dx := t * x
			// log.Println(d, t, dy, dx)
			if dy-dx > d {
				ans = "NO"
				break
			}
		}
	}
	fmt.Println(ans)
}