#include<stdio.h>
int main(){
	int n,v[800],i,j,k,s=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=0;i<n;++i)
		scanf("%d",&v[i]);
	for(i=0;i<n;++i)
		for(j=i+1;j<n;++j)
			for(k=j+1;k<n;++k)
				if(v[i]+v[j]>=v[k]&&v[j]+v[k]>=v[i]&&v[k]+v[i]>=v[j])
					s++;
	printf("%d\n",s);
	fclose(stdin);
	fclose(stdout);
	return 0;
}