#include<stdio.h>

#define dim 801

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

	int n,i,j,k,a[dim],nr=0;

	scanf("%d", &n);

	for(i=1; i<=n; ++i)

		scanf("%d", &a[i]);

	for(i=1; i<=n-2; ++i)

		for(j=i+1; j<=n-1; ++j)

			for(k=j+1; k<=n; ++k)
			
				if(a[i]+a[j]>=a[k] && a[i]+a[k]>=a[j] && a[j]+a[k]>=a[i])

					++nr;

	printf("%d", nr);

	return 0;
}