#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

template<class Val>
vector<Val> compress(vector<Val> &u, vector<Val> &v) {
    vector<Val> a = u;
    for (int b : v) a.push_back(b);
    sort(a.begin(), a.end());
    a.erase(unique(all(a)), a.end());
    for (int &b : u)
        b = (int)(lower_bound(all(a), b) - a.begin());
    for (int &b : v)
        b = (int)(lower_bound(all(a), b) - a.begin());
    return a;
}

void solve() {

    // 座標圧縮、累積和
    
    int N, K;
    cin >> N >> K;
    vi A(N), B(N);
    rep(i, N) {
        cin >> A[i] >> B[i];
        B[i]++;
    }
    auto C = compress(A, B);

    int M = sz(C);
    vll sm(M);
    rep(i, N) {
        sm[A[i]]++;
        sm[B[i]]--;
    }

    ll k = K;
    rep(i, M - 1) {
        if (sm[i] * (C[i + 1] - C[i]) >= k) {
            cout << C[i] + ((k - 1) / sm[i]) << endl;
            break;
        }

        k -= sm[i] * (C[i + 1] - C[i]);
        sm[i + 1] += sm[i];
    }
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}