import java.util.Scanner; public class Main { public static void main(String args[]){ Scanner cin = new Scanner(System.in); int X = cin.nextInt(); int Y = cin.nextInt(); int N = cin.nextInt(); int A[] = new int[N]; long sum = 0L; boolean result = true; double rate = (Y-X)/X; for(int i=1;i<=N;i++){ A[i-1] = cin.nextInt(); if(i>1){ if(sum*rate>(double)A[i-1]){ result = false; break; } } sum += (long)A[i-1]; } if(result){ System.out.println("YES"); }else{ System.out.println("NO"); } } }