## https://yukicoder.me/problems/no/3422

def solve(ab, k, M):
    if k == 0:
        return False

    d = 0
    for i in range(len(ab)):
        x = ab[i]
        d = i // k
        if x <= d:
            return False
    
    return True
        


def main():
    N, M = map(int, input().split())
    ab = []
    for _ in range(N):
        a, b = map(int, input().split())
        ab.append((a, b))

    ab2 = []
    for a, b in ab:
        m = M - a    
        x = m // b
        x += 1
        ab2.append(x)
    ab2.sort()

    low = 0
    high = M
    while high - low > 1:
        mid = (high + low) // 2
        if solve(ab2, mid, M):
            high = mid
        else:
            low = mid
    
    if solve(ab2, low, M):
        print(low)
    else:
        print(high)








    



if __name__ == "__main__":
    main()