#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> lpair;
const ll MOD = 1e9 + 7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i = (m); i < (n); i++)
#define rrep(i,m,n) for(ll i = (m); i >= (n); i--)
#define print(x) cout << (x) << endl;
#define print2(x,y) cout << (x) << " " << (y) << endl;
#define printa(x,n) for(ll i = 0; i < n; i++){ cout << (x[i]) << " ";} cout<<endl;
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N,K;
    cin >> N >> K;
    ll A[100010], B[100010];
    rep(i,0,N) cin >> A[i] >> B[i];
    map<ll,ll> mp;
    rep(i,0,N){
        mp[A[i]]++;
        mp[B[i]+1]--;
    }
    ll lv = 0, rv = 1e9+7;
    while(rv - lv > 1){
        ll mid = (lv + rv) / 2;
        ll v = 0;
        rep(i,0,N){
            if(B[i] <= mid){
                v += B[i] - A[i] + 1;
            }else if(A[i] <= mid && B[i] > mid){
                v += mid - A[i] + 1;
            }
        }
        if(v >= K){
            rv = mid;
        }else{
            lv = mid;
        }
    }
    print(lv+1);
}