n, m = map(int, input().split())
t, p = 0, 0
flag = 0
for i in range(m):
    T, P = map(int, input().split())
    if (T - t) < (P - p):
        flag = 1
    else:
        t = T
        p = P
if flag == 0:
  print("Yes")
else:
  print("N0")