#include<stdio.h>
FILE *f,*g;
int n,v[800],nr,i,j,k;
int main()
{
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(j=i+1;j<=n-1;j++)
for(k=j+1;k<=n;k++)
if(v[i]+v[k]>=v[j] && v[i]+v[j]>=v[k] && v[j]+v[k]>=v[i])
nr++;
fprintf(g,"%d",nr);
return 0;
}