func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, k, a[(int)2e5];   long long sum;   double d, res;   int main() {     cin >> n >> k;     for (int i = 0; i < n; ++i) {       cin >> a[i];       if (i < k) sum += a[i];     }     d = n - k + 1;     res += sum / d;     for (int i = k; i < n; ++i) {       sum -= a[i - k];       sum += a[i];       res += sum / d;     }     cout << fixed << setprecision(6) << res;     return 0;   }   