# include <stdio.h>
int main (){
	int n,i,j,a[801],k,nr=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	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]) 
					if(a[i]+a[k]>=a[j]) 
						if(a[k]+a[j]>=a[i])
							nr++;
			}
	printf("%d",nr);
	return 0;
}