#include <bits/stdc++.h>   using namespace std;   long long int n, u, a[300001], x, y;   long double ans = -1.0;   int main() {     cin >> n >> u;     for (int i = 0; i < n; ++i) cin >> a[i];     y = 1;     while (x < n - 2) {       while (y < n - 1 && a[y + 1] - a[x] <= u) ++y;       if (y - x >= 2 && a[y] - a[x] <= u)         ans =             max(ans, (long double)(a[y] - a[x + 1]) / (long double)(a[y] - a[x]));       ++x;     }     printf( %.9Lf n , ans);     return 0;   }   