#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) printf(__VA_ARGS__)

int dxy[] = {0, 1, 0, -1, 0};

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/

int N,K;

map<int, int> M;

void solve() {
    cin>>N>>K;
    int a,b;
    REP(i,N) {
        cin>>a>>b;
        M[a]++;
        M[b+1]--;
    }
    int c = 1;
    int num = 0;
    for (auto p:M) {
        int price = p.first;
        int add = num * (price - c);
        if (add < K) K -= add;
        else {
            int p = (K-1)/num;
            cout << c + p << endl;
            return;
        }
        c = price;
        num += p.second;
    }
    int p = (K-1)/num;
    cout << c + p << endl;
}