N, W = map(int, input().split())
vw = [list(map(int, input().split())) for _ in range(N)]

max_v = 0
for i in range(N):
    if vw[i][1] <= W:
        max_v = max(max_v, vw[i][0])

if max_v == 0:
    print(-1)
else:
    print(max_v)