#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>inline int popcount(T a) {return __builtin_popcount(a);}
//-------------------
constexpr int MX = 1e5+3;
ll a[MX];
ll b[MX];
int main() {
    cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15);
    ll n,k; cin >> n >> k;
    
    rep(i,n) cin >> a[i] >> b[i];

    ll left = 1, right = 1e9;
    auto f = [&](ll cur) {
        ll res = 0;
        rep(i,n) {
            if(a[i] <= cur) res += (min(cur, b[i])-a[i]+1);
        }
        return res;
    };
    rep(_,100) {
        ll mid = (left+right)/2;
        // cout << left << " " << mid << " " << right << endl;
        if(f(mid) >= k) right = mid;
        else left = mid;
    }

    cout << right << endl;
    return 0;
}