#include <stdio.h>
int n,v[801],i,j,k,t,nr;
int main() {
	FILE *f=fopen("nrtri.in","r");
	FILE *g=fopen("nrtri.out","w");
	fscanf(f,"%d",&n);
	for(i=1;i<=n;i++)
		fscanf(f,"%d",&v[i]);
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			if(v[i]>v[j]) {
				t=v[i];
				v[i]=v[j];
				v[j]=t;
			}
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			for(k=j+1;k<=n;k++)
				if(v[i]+v[j]>=v[k])
					nr++;
	fprintf(g,"%d",nr);
	return 0;
}