#include <stdio.h>


int n,a[802],sum=0;


void quicksort(int lo,int hi){
int h,i=lo,j=hi,x=a[lo+(hi-lo)/2];

do{
	while(a[i]<x){i++;}
	while(a[j]>x){j--;}

	if(i<=j){
		h=a[i];
		a[i]=a[j];
		a[j]=h;
		i++;j--;}}while(i<j);

		if(lo<j){quicksort(lo,j);}
		if(i<hi){quicksort(i,hi);}

}


void bs(int lo,int p){
int hi=n,mid,er=lo-1;

while(lo<hi){
mid=lo+(hi-lo+1)/2;

if(a[mid]<=p){lo=mid;}
else{hi=mid-1;}

}

if(a[lo]<=p){sum+=lo-er;}

}

int main(){
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int i,j;
	scanf("%d",&n);
	for(i=1;i<=n;i++){scanf("%d",&a[i]);}
	
	quicksort(1,n);
	
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
			bs(j+1,a[i]+a[j]);

		printf("%d",sum);


	return 0;}