#include <cstdio>
int a[805];
int main () {
	int n, i, j, k, c=0;
	freopen("ntri.in","r",stdin);
	freopen("ntri.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]&&a[i]+a[k]>=a[j]&&a[j]+a[k]>=a[i]){
					c=c+1;
				}
			}
		}
	}
	printf ("%d",c);
	 return 0;
}