N, H = map(input().split())
D = [[0, 0] for i in range(2 * N)]
for i in range(N):
  a, b = map(int, input().split())
  D[2 * i] = [a, 2]
  D[2 * i + 1] = [b, 1]
D.sort(reverse=True)
cnt = 0
while H > 0:
  d = D[0]
  D = D[1:]
  if d[1] == 1:
    H -= d[0]
    cnt += 1
  else:
    k = -(-H // d[0])
    H -= d[0] * k
    cnt += k
print(cnt)