#include <stdio.h>
#include <stdlib.h>
int v[801],n;
int comp(const void *a, const void *b){
	return *(int*)a-*(int*)b;
}
int caut_y(int poz,int c){
	int m,st,dr;
	st=poz;
	dr=n;
	while(st<=dr){
		m=(st+dr)/2;
		if(v[m]<=c && (v[m+1]>c || m==n))
			return m;
		else if(v[m]<=c) st=m+1;
		else dr=m-1;
	}
	return -1;
}

int main(){
	int i,j,x,y,sol=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		scanf("%d",&v[i]);
	v[0]=0;
	qsort(v,n+1,sizeof(v[0]),comp);
	for(i=1;i<n-1;i++)
		for(j=i+1;j<n;j++){
			y=caut_y(j+1,v[i]+v[j]);
			if(y>0) sol+=y-j;
		}
	printf("%d",sol);
	return 0;
}