#include<bits/stdc++.h>
using lint=long long;
using real=long double;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint n,k;std::cin>>n>>k;k--;
    std::vector<std::pair<lint,lint>>a;
    while(n--){
        lint x,y;std::cin>>x>>y;
        a.emplace_back(x,+1);
        a.emplace_back(y+1,-1);
    }
    std::sort(a.begin(),a.end());
    n=a.size();
    for(lint i=0,m=0,cum=0;i<n-1;i++){
        m+=a.at(i).second;
        lint aug=m*(a.at(i+1).first-a.at(i).first);
        if(k<=cum+aug){
            std::cout<<a.at(i).first+(k-cum)/m<<'\n';
            return 0;
        }
        cum+=aug;
    }
}