#include<stdio.h>
#include<stdlib.h>
int v[1000],n,i,j,r;
int cmp(const void*a,const void*b)
	{return *(int*)a-*(int*)b;}
int main()
{int k;
 FILE*f=fopen("nrtri.in","r");
 FILE*g=fopen("nrtri.out","w");
 fscanf(f,"%d",&n);
 for(i=0;i<n;i++)
	fscanf(f,"%d",&v[i]);
 qsort(v,n,sizeof(v[0]),cmp);
 for(i=0;i<n-2;i++)
	for(j=i+1;j<n-1;j++)
		{k=j+1;
		 while(v[k]<=v[i]+v[j]&&k<n) {r++;
					      k++;}}
 fprintf(g,"%d",r);
 fcloseall();
 return 0;
}