#include<stdio.h>
int main()
{int v[801],i,k=0,p,r,n;
FILE *f,*g;
f=fopen("nrtri.in","r");
g=fopen("nrtri.out","w");
fscanf(f,"%d",&n);
for (i=1; i<=n;i++)
	fscanf(f,"%d",&v[i]);
for (i=1; i<=n-2;i++)
	  for (r=i+1;r<=n-1;r++)
			for(p=r+1;p<=n;p++)
				if (v[i]+v[p]>=v[r]) if (v[i]+v[r]>=v[p]) if(v[r]+v[p]>=v[i]) k++;
fprintf(g,"%d",k);
fclose(f);
fclose(g);}