#include<bits/stdc++.h>
using namespace std;

int main(){
    long long n,k;
    cin>>n>>k;
    long long a,b;
    vector<pair<long long,long long>> v;
    for(long long i=0;i<n;i++){
        cin>>a>>b;
        v.push_back(make_pair(a,0));
        v.push_back(make_pair(b,1));
    }
    sort(v.begin(),v.end());

    long long c=0;
    long long t=1;
    long long p=0;
    p=v[0].first;
    for(long long i=1;i<v.size();i++){
        if(v[i].second==0){
            c+=(v[i].first-p)*t;
            p=v[i].first-1;
            if(c>=k){
                cerr<<i<<" "<<c<<" "<<t<<" "<<p<<endl;
                long long ans=p-(c-k)/t;
                cout<<ans<<endl;
                return 0;
            }
            t++;
            p=v[i].first;
        }
        else {
            c+=(v[i].first-p+1)*t;
            p=v[i].first;
            if(c>=k){
                cerr<<i<<" "<<c<<" "<<t<<" "<<p<<endl;
                long long ans=p-(c-k)/t;
                cout<<ans<<endl;
                return 0;
            }
            t--;
            p=v[i].first+1;
        }
        cerr<<i<<" "<<c<<" "<<t<<" "<<p<<endl;
    }
}