a,b = map(int, input().split())
ls=[]
c=0
f=False
for i in range(a):
    ls.append(list(map(int, input().split())))
for i in range(a):
    if ls[i][1]<=b:
        c=max(c,ls[i][0])
        f=True
if f==False:
    print(-1)
else:
    print(c)