CodeForces 1084A The Fair Nut and Elevator 题解

A. The Fair Nut and Elevator

time limit per test : 1 second
memory limit per test : 256 megabytes
input : standard input
output : standard output

The Fair Nut lives in 𝑛 story house. 𝑎𝑖 people live on the 𝑖-th floor of the house. Every person uses elevator twice a day: to get from the floor where he/she lives to the ground (first) floor and to get from the first floor to the floor where he/she lives, when he/she comes back home in the evening.It was decided that elevator, when it is not used, will stay on the 𝑥-th floor, but 𝑥 hasn't been chosen yet. When a person needs to get from floor 𝑎 to floor 𝑏, elevator follows the simple algorithm: Moves from the 𝑥-th floor (initially it stays on the 𝑥-th floor) to the 𝑎-th and takes the passenger.Moves from the 𝑎-th floor to the 𝑏-th floor and lets out the passenger (if 𝑎 equals 𝑏, elevator just opens and closes the doors, but still comes to the floor from the 𝑥-th floor).Moves from the 𝑏-th floor back to the 𝑥-th. The elevator never transposes more than one person and always goes back to the floor 𝑥 before transposing a next passenger. The elevator spends one unit of electricity to move between neighboring floors. So moving from the 𝑎-th floor to the 𝑏-th floor requires |𝑎−𝑏| units of electricity.
Your task is to help Nut to find the minimum number of electricity units, that it would be enough for one day, by choosing an optimal the 𝑥-th floor. Don't forget than elevator initially stays on the 𝑥-th floor.

Input

The first line contains one integer 𝑛 (1≤𝑛≤100) — the number of floors.
The second line contains 𝑛 integers 𝑎1,𝑎2,…,𝑎𝑛 (0≤𝑎𝑖≤100) — the number of people on each floor.

Output

In a single line, print the answer to the problem — the minimum number of electricity units.
Examples

Input

3 0 2 1

Output

16

Input

2
1 1

Output

4

Note

In the first example, the answer can be achieved by choosing the second floor as the 𝑥-th floor. Each person from the second floor (there are two of them) would spend 4 units of electricity per day (2 to get down and 2 to get up), and one person from the third would spend 8 units of electricity per day (4 to get down and 4 to get up). 4⋅2+8⋅1=16
In the second example, the answer can be achieved by choosing the first floor as the 𝑥-th floor.

思路

枚举答案，在进行验算即可。

代码

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<string>
#define N 1001
using namespace std;
long long a[N],n,ans=0x7fffffff;
long long _abs(long long k)
{
    if(k>=0) return k;
    else return (0-k); 
}
long long f1(long long x,long long k)
{

    long long ret=_abs(x-k)+k+x-2;
    ret*=(2*a[k]);
    return ret;
}
int main()
{
    scanf("%lld",&n);
    for(long long i=1;i<=n;i++) scanf("%lld",&a[i]);
    for(long long i=1;i<=n;i++)
    {
        long long ls=0;
        for(long long j=1;j<=n;j++) ls+=f1(i,j);
        if(ls<ans) ans=ls;
    }
    printf("%lld\n",ans);
    return 0;
}