#include<bits/stdc++.h>
using namespace std;
#define REP(i,m,n) for(int i=(int)(m) ; i < (int) (n) ; ++i )
#define rep(i,n) REP(i,0,n)

int main(){
    int n,k;
    cin>>n>>k;
    int l[n],r[n];
    rep(i,n)cin>>l[i]>>r[i];
    int ok=1e9+7,ng=0;
    while(ok-ng>1){
        int mid=(ok+ng)/2;
        long long cnt=0;
        rep(i,n){
            if(l[i]>mid)continue;
            cnt+=min(r[i],mid)-l[i]+1;
        }
        if(cnt>=k)ok=mid;
        else ng=mid;
    }
    cout<<ok<<endl;
    return 0;
}