#include<cstdio>
#include<algorithm>
using namespace std;
int n, i, j, k, l[1001], q;
int main()
{
    freopen("nrtri.in", "r", stdin);
    freopen("nrtri.out", "w", stdout);
    scanf("%d", &n);
    for(i=1; i<=n; i++) scanf("%d", &l[i]);
    sort(l+1,l+n+1);
	q=0;
    for(i=1; i<=n-2; i++)
        for(j=i+1; j<=n-1; j++)
			for (k=j+1; k<=n && l[i]+l[j]>=l[k]; k++) q++;
    printf("%d\n", q);
	//fclose(stdin);
	//fclose(stdout);
    return 0;
}