#include<iostream>
#include<iomanip>
#include<limits>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<deque>
#include<stack>
#include<string>
#include<string.h>
#include<vector>
#include<set>
#include<map>
#include<bitset>
#include<stdlib.h>
#include<cassert>
#include<time.h>
#include<bitset>
#include<numeric>
#include<unordered_set>
#include<unordered_map>
#include<complex>
using namespace std;
typedef long long ll;
const int mod = 1e9 + 7;
const ll infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;
#define rep(i,n) for (int i=0; i < (n); i++)
typedef double D;      // 座標値の型。doubleかlong doubleを想定
typedef complex<D> P;  // Point
typedef pair<P, P> L;  // Line
typedef vector<P> VP;
const D EPS = 1e-9;    // 許容誤差。問題によって変える
#define X real()
#define Y imag()
#define LE(n,m) ((n) < (m) + EPS)
#define GE(n,m) ((n) + EPS > (m))
#define EQ(n,m) (abs((n)-(m)) < EPS)
D dot(P a, P b) {
  return (conj(a)*b).X;
}
int main(){
    cout << fixed << setprecision(10);
    int N,K;
    cin >> N >> K;
    vector<int>A(N),B(N);
    rep(i,N)cin >> A[i] >> B[i];
    int L=0,R=(int)1e9+1;
    while(R-L>1){
        int mid=(L+R)>>1;
        ll cn=0;
        rep(i,N){
            if(A[i]>mid)continue;
            cn+=min(B[i],mid)-A[i]+1;
        }
        if(cn>=K)R=mid;
        else L=mid;
    }
    cout << R << endl;
    return 0;
}