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

int v[801];

int main()
{
    int k,j,nr,i,n,x;
    FILE *in,*out;
    in=fopen("nrtri.in","r");
    out=fopen("nrtri.out","w");
    fscanf(in,"%d",&n);
    nr=0;
    for(i=1; i<=n; i++)
    {
        fscanf(in,"%d",&v[i]);
    }
    for(i=1; i<=n; i++)
    {
        for(j=i+1; j<=n; j++)
        {
            for(k=j+1; k<=n; k++)
            {
                if(v[i]+v[j]>=v[k] && v[i]+v[k]>=v[j] && v[j]+v[k]>=v[i])
                {
                    nr++;
                }
            }
        }
    }
    fprintf(out,"%d",nr);
    fclose(in);
    fclose(out);
    return 0;
}