#include<stdio.h>
#include<stdlib.h>

int v[30720], val[1024];

int cmp(const void *a, const void *b)
{
	return *(int *)b - *(int *)a;
}


int main()
{
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out", "w", stdout);

	int n, i, j, k, sol=0;
	
	scanf("%d", &n);
		
	for (i=1; i<=n; i++)
	{
		scanf("%d", &val[i]);
		++v[val[i]];
	}
	
		
	for (i=1; i<=30000; i++)
		v[i]+=v[i-1];
	
	qsort(val+1, n, sizeof(int), cmp);
		
	if (n<100)
	{
		for (i=1; i<n-1; i++)
			for (j=i+1; j<n; j++)
				for (k=j+1; k<=n; k++)
					if (((val[i]<=val[j]+val[k]) && (val[i]>=val[j]) && (val[i]>=val[k])) || ((val[j]<=val[i]+val[k]) && (val[j]>=val[i]) && (val[j]>=val[k])) || ((val[k]<=val[i]+val[j]) && (val[k]>=val[i]) && (val[k]>=val[j])))  sol++;
		printf("%d", sol);
		return 0;
	}
	
	for (i=1; i<n-1; i++)
		for (j=i+1; j<n; j++)
			if (val[i]-val[j] <= val[j]) sol+=v[val[j]] - v[val[i]-val[j]-1]-1 -(val[j]==val[j-1]);
	
	printf("%d", sol);
	return 0;
}