# include <stdio.h>
int main (){
	int n,i,j,a[800],nr=0,aux;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	if (n>=3){
		for(i=0;i<n;i++)
		     scanf("%d",&a[i]);
		for (i=1;i<n;i++){
			aux=a[i];
			j=i-1;
			while (j>0 && aux<a[j]){
				a[j+1]=a[j]; 
				j--;
			}
			if (aux>=a[j]) 
				a[j+1]=aux;
				  else{
					a[1]=a[0];
					a[0]=aux;
					}
          }
        for(i=0;i<n-2;i++)
			for(j=i+2;j<n && a[j]<=a[i]+a[i+1];j++)
		  		if(a[i]+a[j]>=a[i+1] && a[i+1]+a[j]>=a[i])
					nr++;
	}
   printf("%d\n",nr);
	return 0;
}