Gerald got a very curious hexagon for his birthday. The boy found out that all the angles of the hexagon are equal to . Then he measured the length of its sides, and found that each of them is equal to an integer number of centimeters. There the properties of the hexagon ended and Gerald decided to draw on it.

He painted a few lines, parallel to the sides of the hexagon. The lines split the hexagon into regular triangles with sides of 1 centimeter. Now Gerald wonders how many triangles he has got. But there were so many of them that Gerald lost the track of his counting. Help the boy count the triangles.

The first and the single line of the input contains 6 space-separated integers a₁, a₂, a₃, a₄, a₅ and a₆ (1 ≤ a_i ≤ 1000) — the lengths of the sides of the hexagons in centimeters in the clockwise order. It is guaranteed that the hexagon with the indicated properties and the exactly such sides exists.

Print a single integer — the number of triangles with the sides of one 1 centimeter, into which the hexagon is split.

This is what Gerald's hexagon looks like in the first sample:

And that's what it looks like in the second sample:

题意：给出一个六边形，求它由多少个小三角形组成

首先要知道，一个大的等边三角形由它的边长乘以边长个小三角形组成，那么给六边形加上三个三角形就可以形成一个大的等边三角形，最后就好求了吧

#include"iostream"

#include"cstdio"

using namespace std;

int main()

{

    int a1,a2,a3,a4,a5,a6;

    cin>>a1>>a2>>a3>>a4>>a5>>a6;

    int l=a1+a2+a3;

    cout<<l*l-a1*a1-a3*a3-a5*a5<<endl;

    return ;

}