#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define se second
int main(){
    int n,k;
    cin >> n >> k;
    vector<pair<int,int>> v(n);
    for(int i=0;i < n;i++)
    {
        cin >> v.at(i).fi >> v.at(i).se;
    }//input

    int no=0,yes=pow(10,9);

    while(abs(no-yes)>1){
        int cnt=0,c=(no+yes)/2;
        for(int i=0;i < n;i++)
        {   
            cnt+=min(c,v.at(i).se)-min(v.at(i).fi,c)+1;
            if(cnt>=k){
                yes=c;
                break;
            }
        }
        if(cnt<k){
            no=c;
        }
    }

    cout << yes << endl;
}
//queue 要素多すぎるとMLE