N, HP = map(int, input().split())

hit = 0
throw = []
for i in range(N):
    h, t = map(int, input().split())
    if h > hit:
        hit = h
    throw.append(t)

throw.sort()


ans = 0
for t in throw[::-1]:
    if t < hit:
        break
    else:
        ans += 1
        HP -= t
        if HP <= 0:
            break

ans += (HP * 100) // (hit * 100)
print(ans)