#include <stdio.h>
#include <stdlib.h>

FILE *fin, *fout;

int compare (const void * a, const void * b)
{
  return ( *(int*)a - *(int*)b );
}

int main()
{
    fin = fopen ("nrtri.in", "r");
    fout = fopen ("nrtri.out", "w");

    int n,v[801],i,j,k,nr=0;

    fscanf(fin,"%d", &n);

    for(i=0;i<n;++i)
        fscanf(fin, "%d", &v[i]);

    qsort (v, n, sizeof(int), compare);

    //O(n^3)

    for(i=0;i<n-2;++i)
        for(j=i+1;j<n-1;++j)
            for(k=j+1;k<n;++k)
            {
                //fprintf(fout, "%d %d %d \n", v[i], v[j], v[k]);
                if(v[k]>v[i]+v[j]) break;
                if(v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i]) nr++;
            }

    fprintf(fout,"%d\n", nr);

    fclose(fin);
    fclose(fout);

    return 0;
}