#include<stdio.h>
#include<algorithm>
using namespace std;
FILE *fin,*fout;
int n,number;
bool triangle(int a,int b,int c)
{
    return a+b>=c;
}
int main()
{
    fin=fopen("nrtri.in","r");
    fout=fopen("nrtri.out","w");
    fscanf(fin,"%d",&n);
    int v[n+1];
    for(int i=0; i<n; i++) fscanf(fin,"%d",&v[i]);
    sort(v,v+n);
    for(int i=0; i<n-2; i++)
        for(int j=i+1; j<n-1; j++)
            for(int k=j+1;k<n; k++)
            {
                if(triangle(v[i],v[j],v[k])) number++;
                else break;
            }
    fprintf(fout,"%d",number);
}