#include <bits/stdc++.h>   using namespace std;   int n, a[3005], b[3005], df[3005];   long long F[3005][3005];   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     cin >> n;     for (int i = 1; i <= n; ++i) {       cin >> a[i];       a[i] = a[i] - i;       b[i] = a[i];     }     sort(b + 1, b + n + 1);     int m = 0;     b[0] = b[1] - 1;     for (int i = 1; i <= n; ++i) {       if (b[i] > b[i - 1]) df[++m] = b[i];     }     for (int i = 1; i <= n; ++i)       for (int j = 0; j <= m; ++j) {         F[i][j] = 1e18;       }     for (int i = 1; i <= n; ++i) {       for (int j = 1; j <= m; ++j) {         F[i][j] = min(F[i][j - 1], F[i - 1][j] + abs(a[i] - df[j]));       }     }     long long rs = 1e18;     for (int i = 1; i <= m; ++i) rs = min(rs, F[n][i]);     cout << rs;     return 0;   }   