var A,B,C,N,i,j,m,k:integer;
    rezerva:array[1..810] of integer;
Begin
      assign(input,'nrtri.in'); reset(input);
      assign(output,'nrtri.out'); rewrite(output);
      readln(input,n);
      for i:=1 to n do read(input,rezerva[i]);
      m:=0;
       for i:=1 to n-2 do
        for j:=i+1 to n-1 do
         for k:=j+1 to n do
         begin
              A:=rezerva[i]; B:=rezerva[j]; C:=rezerva[k];
              if (A+B>=C) and (A+C>=B) and (B+C>=A) then inc(m);
         end;
      write(output,m);
      close(input);
      close(output);
End.