#include<stdio.h>
#include<stdlib.h>
int comp(const void *a, const void *b){
	int *aa=(int *)a, *bb=(int *)b;
	int x=*aa, y=*bb;
	return x-y;
}
int main () {
	int n,v[800],i,nr=0,j,k,s;
	FILE *in=fopen("nrtri.in","r"), *out=fopen("nrtri.out","w");
	fscanf(in,"%d",&n);
	for(i=0;i<n;i++)
		fscanf(in,"%d",&v[i]);
	qsort(v,n,sizeof(v[0]),comp);
	for(i=0;i<n-2;i++)
		for(j=i+1;j<n-1;j++){
			s=j+1;
			for(k=s;k<n;k++)
				if((v[i]+v[j])>=v[k]){
					nr++;
					s=k+1;
				}
		}
	fprintf(out,"%d\n",nr);
	fclose(in);
	fclose(out);
	return 0;
}