#include <bits/stdc++.h>   using namespace std;   int N;   int A[100005];   int G[100005];   int m;   int main() {     scanf( %d , &N);     for (int i = 0; i < N; ++i) scanf( %d , &A[i]);     for (int i = 0; i < N; ++i) {       if (i < N / 2) {         if (A[i] - i >= 1) ++G[A[i] - i];       } else {         if (A[i] - (N - i - 1) >= 1) ++G[A[i] - (N - i - 1)];       }     }     m = 0;     for (int i = 0; i <= 1e5; ++i)       if (G[i] >= m) m = G[i];     printf( %d , N - m);     return 0;   }   