n,k = map(int,input().split())
ab = [[int(i) for i in input().split()] for j in range(n)]
#for K in range(1,14+1):
    #n,k = map(int,input().split())
    #ab = [[int(i) for i in input().split()] for j in range(n)]
    #print(K,K,K)
a = []

for i in range(n):
    a.append(ab[i][0])
    a.append(ab[i][0]+1)
    a.append(ab[i][1])
    a.append(ab[i][1]+1)

asrt = sorted(set(a))
adt = { v: i for i, v in enumerate(asrt) }
#adt[a[i]]#で座圧完了！！！

li = [0]*(len(adt)+1)

for i in range(n):
    li[adt[ab[i][0]]] += 1
    li[adt[ab[i][1]]+1] -= 1

rui = [0]*(len(adt)+1)
#print(asrt)

for i in range(1,len(adt)+1):
    rui[i] = rui[i-1]+li[i-1]
#print(rui,adt)
#exit()
for i in range(1,len(adt)):
    if k <= rui[i]*(asrt[i]-asrt[i-1]):
        print(asrt[i-1]+(k-1)//rui[i])
        #print(i,i,i,asrt[i])
        break
    else:
        k -= rui[i]*(asrt[i]-asrt[i-1])
        #print(k,i,i,i,i)

#print(asrt[len(asrt)-1])