#include <bits/stdc++.h>
#define x first
#define y second

using PII = std::pair<int, int>;

const int N = 100010;
int ans = 1e9;
PII a[N];

int main() {
	freopen("double_muscle.in", "r", stdin);
	freopen("double_muscle.out", "w", stdout);
	int n, m;
	std::cin >> n >> m;
	for (int i = 1; i <= n; ++ i)
		std::cin >> a[i].x >> a[i].y;
	std::sort(a + 1, a + 1 + n, [](PII a, PII b) {
		return a.y < b.y;
	});
	for (int i = 1; i <= n; ++ i)
		for (int j = i + 1; j <= n; ++ j)
			if (a[j].y - a[i].y >= m)
				ans = std::min(ans, std::abs(a[i].x - a[j].x));
	std::cout << ans << '\n';
	return 0;
}