#include <bits/stdc++.h>   using namespace std;   int e[100010];   int main() {     int n, u, i, j = 3;     double ans = 0;     scanf( %d%d , &n, &u);     for (i = 1; i <= n; i++) scanf( %d , &e[i]);     for (i = 1; i <= n; i++) {       while (j <= n && e[j] - e[i] <= u) j++;       j--;       if (j > i + 1) ans = max(ans, (e[j] - e[i + 1] + 0.0) / (e[j] - e[i]));     }     if (ans == 0)       cout << -1 << endl;     else {       cout.precision(19);       cout << ans << endl;     }     return 0;   }   