Calculate the formula

Problem Description

You just need to calculate the sum of the formula: 1^2+3^2+5^2+……+ n ^2.

 

Input

In each case, there is an odd positive integer n.

 

Output

Print the sum. Make sure the sum will not exceed 2^31-1

 

Sample Input

3

 

Sample Output

10

 

用普通的做法会超时，只能用公式算n*(4*n*n-1)/3(其中n为第几个数)，还有题目明明说好结果在int范围内的，但是必须用__int64才能过，郁闷。。。

 

#include <stdio.h>

int main(){
    __int64 number;
    __int64 n;
    __int64 result;

    while(scanf("%I64d",&number)!=EOF){
        n=(number+1)/2;

        result=n*(4*n*n-1)/3;
        printf("%I64d\n",result);

    }
    return 0;
}