#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long ll;
int n,t;
vector<int> v;
inline ll Abs(ll x) {
return x>0?x:-x;
}
ll calc(ll p) {
ll ret = 0;
for(int i=1;i<n;i++) ret += Abs(v[i]-i*p);
return ret;
}
int search(int front,int rear) {
if(front == rear) return front;
int mid = (front + rear) / 2;
ll first = calc(mid);
ll second = calc(mid+1);
if(first < second) return search(front, mid);
return search(mid+1, rear);
}
int main() {
scanf("%d",&n);
for(int i=0;i<n;i++) {
scanf("%d",&t);
v.push_back(t);
}
int M = 0;
for(int i=1;i<n;i++) M = max(M, v[i]/i+1);
int dydx = search(1,M);
ll ans = 0;
for(int i=1;i<n;i++) ans += Abs(v[i]-i*dydx);
printf("%lld\n",ans);
return 0;
}
