#include <stdio.h>

int N, A[1000], B[1000];


void merge_sort(int l, int r)
{
    int m = (l + r) >> 1, i, j, k;
    if (l == r) return;
    merge_sort(l, m);
    merge_sort(m + 1, r);
    for (i=l, j=m+1, k=l; i<=m || j<=r; )
	if (j > r || (i <= m && A[i] < A[j]))
	    B[k++] = A[i++];
	else
	    B[k++] = A[j++];
    for (k = l; k <= r; k++) A[k] = B[k];
}

int main()
{ int i,nr=0,j,k;
freopen("nrtri.in","rt",stdin);
freopen("nrtri.out","wt",stdout);
scanf("%d",&N);
for (i=1;i<=N;i++)
    scanf("%d",&A[i]);
merge_sort(1,N);
for (i=1;i<=N-2;i++)
for (j=i+1;j<=N-1;j++)
for (k=j+1;k<=N;k++)
if (A[k]<=A[i]+A[j] && A[j]<=A[k]+A[i] && A[i]<=A[k]+A[j]) nr++;
printf("%d",nr);
return 0;}