#include<stdio.h>
FILE *f=fopen("nrtri.in","r"), *g=fopen("nrtri.out","w");
long int i,j,l, v[802], n, nrtri=0;

int main(){

	fscanf(f,"%ld\n",&n);
	for(i=1;i<=n;i++){
		fscanf(f,"%ld",&v[i]);
	}
	
	for(i=1;i<=n-2;i++){
		for(j=i+1;j<=n-1;j++){
			for(l=j+1;l<=n;l++){
				if(v[i]+v[j]>=v[l] && v[i]+v[l]>=v[j] && v[j]+v[l]>=v[i]){
					nrtri++;
				}
			}
		}
	}
	fprintf(g,"%ld",nrtri);
	
fclose(f);fclose(g);
return 0;
}