n, W = map(int, input().split())

k = [0] * n

for i in range(n):
    v, w = map(int, input().split())
    k[i] = [v, w]

ans = []
for v, w in k:
    if w <= W:
        ans.append(v)

if len(ans) == 0:
    print(-1)
else:
    print(max(ans))