#include<stdio.h>

FILE *f=fopen("nrtri.in","r"), *g=fopen("nrtri.out","w");

long n,v[800],i,j,k,s;

int main() {
   fscanf(f,"%ld",&n);
   for(i=0;i<n;i++) {
      fscanf(f,"%ld",&v[i]);
   }
   for(i=0;i<n-2;i++)
      for(j=i+1;j<n-1;j++)
	 for(k=j+1;k<n;k++)
	    if(v[i]+v[j]>=v[k] && v[j]+v[k]>=v[i] && v[i]+v[k]>=v[j]) s++;
   fprintf(g,"%ld",s);
   fcloseall();
   return 0;
}