/****************************************************

     Author : Coolxxx

     Copyright 2017 by Coolxxx. All rights reserved.

     BLOG : http://blog.csdn.net/u010568270

 ****************************************************/

 #include<bits/stdc++.h>

 #pragma comment(linker,"/STACK:1024000000,1024000000")

 #define abs(a) ((a)>0?(a):(-(a)))

 #define lowbit(a) (a&(-a))

 #define sqr(a) ((a)*(a))

 #define mem(a,b) memset(a,b,sizeof(a))

 const double EPS=1e-;

 const int J=;

 const int MOD=;

 const int MAX=0x7f7f7f7f;

 const double PI=3.14159265358979323;

 const int N=;

 const int M=;

 using namespace std;

 typedef long long LL;

 double anss;

 LL aans;

 int cas,cass;

 int n,m,lll,ans;

 int e[]={,,,,,,,,,};

 int a[N],b[N];

 int main()

 {

     #ifndef ONLINE_JUDGE

     freopen("1.txt","r",stdin);

 //  freopen("2.txt","w",stdout);

     #endif

     int i,j,k;

     int x,y,z;

 //  for(scanf("%d",&cass);cass;cass--)

 //  for(scanf("%d",&cas),cass=1;cass<=cas;cass++)

 //  while(~scanf("%s",s))

     while(~scanf("%d",&n))

     {

         for(i=;i<=n;i++)

             scanf("%d",&a[i]);

         for(k=;k<;k++)

         {

             for(i=;i<=n;i++)

                 b[i]=a[i]%e[k];

             sort(b+,b++n);

             for(i=;i<=n;i++)

             {

                 int l,r,mid;

                 l=i+,r=n;

                 while(l<=r)

                 {

                     mid=(l+r+)/;

                     if(b[mid]+b[i]<e[k])l=mid+;

                     else r=mid-;

                 }

                 aans+=n-r;

             }

         }

         printf("%lld\n",aans);

     }

     return ;

 }

 /*

 //

 //

 */