/*
 * File:   main.cpp
 * Author: petru
 *
 * Created on 2010-09-21
 */


#include <cstdio>
#include <algorithm>
#define deb(n) fprintf(stderr,"%d ",(n));
#define DN 805
using namespace std;

int n,lg[DN];

int main()
{
	int cont=0;
	freopen("ntri.in","r",stdin);
	freopen("ntri.out","w",stdout);
	scanf("%d",&n);
	for(int i=1; i<=n; ++i) scanf("%d",&lg[i]);
	sort(lg+1,lg+n+1);
	for(int i=1;i<=n-2;++i)
		for(int j=i+1;j<=n-1;++j)
			for(int k=j+1;k<=n;++k)
				if(lg[i]+lg[j]>=lg[k]) ++cont;//triunghiul exista
				else break;
    printf("%d\n",cont);
	return 0;
}