#include<stdio.h>
FILE*A,*B;
int j=0,n,v[810],k=0,aux,i=0,sol=0;
int main()
{
	A=fopen("ntri.in","r");
	B=fopen("ntri.out","w");
	fscanf(A,"%d",&n);
	for(i=1;i<=n;i++)fscanf(A,"%d",&v[i]);
	for(i=1;i<=n-1;i++)
	{
		for(j=1+i;j<=n;j++){if(v[i]>=v[j]){aux=v[i];v[i]=v[j];v[j]=aux;}}
	}
	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[j]<v[k])k=n+1;
				else sol++;
			}
		}
	}
	fprintf(B,"%d",sol);fclose(A);fclose(B);
}