#include<stdio.h>
int main()
{
	int nr=0,i,j,k,n,v[801];\
	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;++k)
				if(v[i]+v[j]>=v[k]&&v[i]+v[k]>=v[j]&&v[j]+v[k]>=v[i])
					++nr;
				printf("%d",nr);
	return 0;
}