View Compilation Error

0_0_37894532_24946.cpp: In function 'void solve()':
0_0_37894532_24946.cpp:25:39: error: invalid types 'double [200010][double]' for array subscript
         double ans = (f[i] - f[i - len]) / len;
                                       ^
0_0_37894532_24946.cpp:26:40: error: invalid types 'double [200010][double]' for array subscript
         double ant = f2[i] - f2[i - len] + len * ans * ans - 2 * ans * (f[i] - f[i - len]);
                                        ^
0_0_37894532_24946.cpp:26:89: error: invalid types 'double [200010][double]' for array subscript
         double ant = f2[i] - f2[i - len] + len * ans * ans - 2 * ans * (f[i] - f[i - len]);
                                                                                         ^