#include <iostream>
#include <cstdint>
#include <vector>

using namespace std;

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

	uint32_t N, W, i;
	cin >> N >> W;
	vector<uint32_t> v(N), w(N);
	for (i = 0; i != N; ++i) cin >> v[i] >> w[i];

	uint32_t ans = 0;
	for (i = 0; i != N; ++i)
		if (w[i] <= W && ans < v[i])
			ans = v[i];

	if (ans == 0) cout << "-1\n";
	else cout << ans << '\n';

	return 0;
}