#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n,k;
  cin>>n>>k;
  vector<Int> a(n),b(n);
  for(Int i=0;i<n;i++) cin>>a[i]>>b[i],b[i]++;

  auto check=
    [&](Int x)->Int{
      Int res=0;
      for(Int i=0;i<n;i++){
        if(a[i]<x) res+=min(b[i],x)-a[i];
      }
      return res<k;
    };
  
  Int l=0,r=1e9+1;
  while(l+1<r){
    Int m=(l+r)>>1;
    if(check(m)) l=m;
    else r=m;
  } 
  cout<<l<<endl;
  return 0;
}