import sys
from math import sqrt
inp = lambda : sys.stdin.readline()[:-1]
mii = lambda x = " ": [*map(int,input().split(x))]
mfi = lambda x = " ": [*map(float,input().split(x))]
ii = lambda : int(input())
h, w, n = mii()
l = mii()
crt = 0
cnt = 0
for i in l:
crt += i
if crt > w:
print("NO")
break
if crt == w:
cnt += 1
crt = 0
if cnt >= h:
print("YES")
break