var a:array[1..800] of word; n,i,j,k,x,aux:word; fi,fo:text;
begin assign(fi,'nrtri.in'); reset(Fi);
      assign(Fo,'nrtri.out'); rewrite(fo);
      readln(fi,n);
      for i:=1 to n do
      read(fi,a[i]);
      for i:=1 to n-1 do
                for j:=i+1 to n do
                    if a[i]>a[j] then begin
                                         aux:=a[i];
                                         a[i]:=a[j];
                                         a[j]:=aux;
                                        end;
      x:=0;

      for i:=1 to n-2 do
                        for j:=i+1 to n-1 do
                                for k:=j+1 to n do
                                                if (a[j]+a[k]>=a[i]) and (a[i]+a[j]>=a[k]) and (A[i]+a[j]>=a[j]) then inc(x);
      writeln(fo,x);
      close(Fi); close(Fo);
end.