N, W = map(int, input().rstrip().split(" "))  # nは入力回数
vw_list = [list(map(int, input().split())) for _ in range(N)]

max_v = 0
max_v_dict = {}
w_list = []
for i in sorted(vw_list, key=lambda x: x[1]):
    if i[0] > max_v:
        max_v = i[0]
    max_v_dict[i[1]] = max_v
    w_list.append(i[1])

if W < w_list[0]:
    print(-1)
    exit()

while True:
    c_idx = int(len(w_list) / 2)
    if W < w_list[c_idx]:
        w_list = w_list[:c_idx]
        if W > w_list[-1]:
            print(max_v_dict[w_list[-1]])
            exit()
    else:
        w_list = w_list[c_idx:]
        if len(w_list) == 1 or W < w_list[1]:
            print(max_v_dict[w_list[0]])
            exit()