#include <bits/stdc++.h>

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = std::int64_t;
using P = std::tuple<int,int>;

int N, K;
int A[100100], B[100100];

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    std::cin >> N >> K;

    for(int i=0;i<N;++i){
        std::cin >> A[i] >> B[i];
    }

    int lb = 0, ub = 1001001001;

    while(ub - lb > 1){
        int m = (lb + ub) / 2;

        ll cnt = 0;

        for(int i=0;i<N;++i){
            if(A[i] <= m){
                cnt += std::min(B[i], m) - A[i] + 1;
            }
        }

        if(cnt >= K){
            ub = m;
        }else{
            lb = m;
        }
    }

    std::cout << ub << std::endl;
}