#include <stdio.h>
#define N 812
char v[N];
int main()
{
	int rez=0,i,j,k,n;
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out", "w",stdout);
	scanf("%d", &n);
	for(i=1;i<=n;++i)
		scanf("%d", &v[i]);
	for(i=1;i<=n;++i)
		for(j=i+1;j<=n;++j)
			for(k=j+1;k<=n;++k)
				if(v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i])
					++rez; 
	printf("%d\n", rez);
	return 0;
}