#include <stdio.h>
int v[800];

int main()
{
    FILE *in,*out;
    int n,i,j,min,nrmin,temp,nr=0,ii;
    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]);
    }
    for(i=0;i<n;i++)
    {
        min=999999;
        nrmin=0;
        for(j=i;j<n;j++)
        {
            if(v[j]<min)
            {
                min=v[j];
                nrmin=j;
            }
        }
        temp=v[i];
        v[i]=v[nrmin];
        v[nrmin]=temp;
    }
    for(i=0;i<n-2;i++)
    {
        for(j=i+1;j<n-1;j++)
        {
            for(ii=j+1;ii<n;ii++)
            {
                if(v[i]+v[j]<v[ii])
                    ii=n;
                else
                    nr++;
            }
        }
    }
    fprintf(out,"%d",nr);
    return 0;
}