#include<stdio.h>
int main(){
	int n,v[801],i,j,k,s=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for (i=0;i<n;++i)
		scanf("%d",&v[i]);
	for (i=0;i<n-2;++i)
		for (j=i+1;j<n-1;++j)
			for (k=j+1;k<n;++j)
				if ((v[i]+v[j]>=v[k])&&(v[j]+v[k]>=v[i])&&(v[k]+v[i]>=v[j]))
					++s;
	printf("%d",s);
	return 0;
}