# include <stdio.h>
int main (){
	int n,i,j,a[800],b[800],k,nr=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=0;i<n;i++)
		scanf("%d",&a[i]);
	for(i=0;i<n;i++);
		for(j=i;j<n;j++)
			for(k=j;k<n;k++)
				if(a[i]+a[j]>=a[k] && a[i]+a[k]>=a[j] && a[k]+a[j]>=a[i]){
					b[i]=a[i];
					b[j]=a[j];
					b[k]=a[k];
					nr++;
				}
	printf("%d",nr);
	return 0;
}