#include <cstdio>
#include <fstream>

using namespace std;

#define N 7005

int c[N];

int main ()
{
	ifstream in ("medie.in");
	int n,x,m=0;
	for(in>>n;n;--n){
		in>>x;
		++c[x];
		if(x>m)
			m=x;
	}
	in.close ();
	long long S=0;
	for(int i=1;i<=m;++i)
		if(c[i]){
			if(c[i]>2)
				S+=(((c[i]-2)*(c[i]-1)*c[i])>>1);
			for(int j=i-1,k=i+1;j&&k<=m;++k,--j)
				S+=c[i]*c[j]*c[k];
			}
	freopen ("medie.out","w",stdout);
	printf("%lld\n",S);
	
	return 0;}