#include"bits/stdc++.h"

using namespace std;
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

#define FOR(k,m,n) for(ll (k)=(m);(k)<(n);(k)++)
#define REP(i,n) FOR((i),0,(n))
#define WAITING(str) int str;std::cin>>str;
#define DEBUGING(str) cout<< #str << " " str<<endl

constexpr int INF = (1 << 30);
constexpr ll INFL = (1ll << 60);
constexpr ll MOD = 1000000007;// 10^9+7



int main()
{
	ll N, K;
	cin >> N >> K;
	vector<pair<ll, ll>> abs(N);
	REP(i, N) {
		ll a, b;
		cin >> a >> b;
		abs[i] = { a,b };
	}
	sort(abs.begin(), abs.end());

	ll l = 0, r = 1e9 + 10;
	while (r - l > 1) {
		ll mid = (l + r) / 2;
		ll num = 0;
		for (auto ab : abs) {
			ll a = ab.first;
			ll b = ab.second;
			if (mid < a)continue;
			if (b < mid) {
				num += (b - a + 1);
			}
			else {
				num += (mid - a + 1);
			}
		}
		if (num < K)l = mid;
		else r = mid;
	}
	cout << r << endl;
	return 0;
}