#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	int N, W;
	cin >> N >> W;

	int v, w;
	int ans = 0;

	for (int i = 0; i < N; i++) {
		cin >> v >> w;
		if (w <= W) {
			if (v > ans) {
				ans = v;
			}
		}
	}

	if (ans != 0) {
		cout << ans << endl;
	}
	else {
		cout << -1 << endl;
	}

	return 0;

}