#include<stdio.h>
#include<stdlib.h>
int a, b, j, v[801], nr, n;
int comp(const void*x, const void*y)
{
	int *xx=(int*)x, *yy=(int*)y;
	int xxx=*xx, yyy=*yy;
	if (xxx<yyy) return -1;
	if (xxx>yyy) return 1;
	return 0;
}
int bs(){
	int li=j+1, ls=n, t;
	while (li<=ls){
		t=(li+ls)/2;
		if (v[t]>a+b)
			ls=t-1;
		else 
		if (v[t+1]>a+b||t==n)
			return t;
		else 
			li=t+1;
	}
	return 0;
}
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int i, poz;
	scanf("%d",&n);
	if (n==1||n==2)
		printf("0\n");
	else {
		for (i=1;i<=n;i++)
			scanf("%d",&v[i]);
		qsort(v,n+1,sizeof(v[0]),comp);
		v[n+1]=30001;
		for (i=1;i<n-1;i++)
			for (j=i+1;j<n;j++)
			{
				a=v[i];
				b=v[j];
				poz=bs();
				if (poz!=0)
					nr+=poz-j;
			}
		printf("%d\n",nr);
	}
	fclose(stdin);
	fclose(stdout);
	return 0;
}