先暴力把1~20的结果打出来...观察..发现都是两个互质的数乘积...那么就从x/2开始找互质的数...10^9也可以秒出....不知道如何证明..


Program:

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<cmath>
#include<queue>
#include<stack>
#include<set>
#include<algorithm>
#define ll long long
#define oo 1000000007
#define pi acos(-1.0)
#define MAXN 100005
using namespace std;    
ll gcd(ll a,ll b)
{
       while (b)
       {
             ll k=a;
             a=b,b=k%b;
       }
       return a;
}
int main()
{       
       ll t,x,p;  
       scanf("%I64d",&t);
       while (t--)
       { 
               scanf("%I64d",&x);
               p=x/2;
               while (gcd(p,x-p)!=1) p--;
               printf("%I64d\n",p*(x-p));
       }
       return 0;
}