#include<bits/stdc++.h>
#define REP(i,n) for(int i=0;i<(n);i++)
#define ALL(v) (v).begin(),(v).end()
#define SZ(x) ((int)(x).size())
#define int long long
using namespace std;
typedef vector<int>   vint;
typedef pair<int,int> pint;

int N,K;
vint a,b;

bool check(int x)
{// x以下の数がK個数以上あるか
    int cnt=0;
    REP(i,N){
        if(a[i]<=x and x<=b[i]) cnt+=x-a[i]+1;
        else if(b[i]<x) cnt+=b[i]-a[i]+1;
    }
    return cnt>=K;
}

signed main()
{
    cin>>N>>K;
    a.resize(N);
    b.resize(N);
    REP(i,N) cin>>a[i]>>b[i];
    
    int ng=0,ok=1e9;
    while(ok-ng>1){
        int mid=(ok+ng)/2;
        if(check(mid)) ok=mid;
        else ng=mid;
    }
    cout<<ok<<endl;
}