n,k=map(int,input().split())
x={};y={}
v=[];s=set()
for i in range(n):
    a,b=map(int,input().split())
    s.add(a);s.add(b+1)
    v.append((a,b+1))
p=0
for i in sorted(list(s)):
    x[i]=p;y[p]=i;p+=1
m=[0]*len(s)
for i,j in v:
    m[x[i]]+=1;m[x[j]]-=1
for i in range(len(s)-1):
    c=y[i+1]-y[i]
    m[i+1]+=m[i]
    if m[i]*c>=k:
        print(y[i]+(k-1)//m[i])
        break
    k-=m[i]*c