t = int(input())
arr = list(map(int, input().split()))
ans = float("inf")
for i in range(t):
floor = i
count = 0
for j in range(len(arr)):
new = abs(j - floor)
new += j
new += floor
new *= 2
new *= arr[j]
count+= new
ans = min(ans, count)
print(ans)#include <bits/stdc++.h>
using namespace std;
int main(){
int n;
scanf("%d", &n);
int a[n];
for(int i = 0; i < n; i++){
scanf("%d", a+i);
}
int x = 1e9;
for(int f = 0; f < n; f++){
int y = 0;
for(int i = 0; i < n; i++){
int cost = abs(f - i) + i + f;
cost += cost;
y += cost * a[i];
}
x = min(x, y);
}
printf("%d\n", x);
return 0;
}
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