a,b = map(int,input().split())
c = {}
for i in range(b):
p,q = map(int,input().split())
if p not in c:
c[p] = list()
c[p].append(q)
r = sorted(c)
for i in r:
if i >= a:
print("NO")
break
else:
a += sum(c[i])
print("YES")
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