#include <bits/stdc++.h>   using namespace std;   int a[100005];   int l[100005];   int r[100005];   int main() {     int n;     cin >> n;     for (int i = 1; i <= n; i++) {       scanf( %d , &a[i]);     }     for (int i = 1; i <= n; i++) {       l[i] = min(l[i - 1] + 1, a[i]);     }     for (int i = n; i >= 1; i--) {       r[i] = min(r[i + 1] + 1, a[i]);     }     int ma = 0;     for (int i = 1; i <= n; i++) {       ma = max(ma, min(l[i], r[i]));     }     cout << ma << endl;   }   