var A,B,C,N,i,j,m,k:integer;
    rezerva:array[1..810] of integer;


function verificare(i,j,k:integer):boolean;
begin
    verificare:=true;
    A:=rezerva[i]; B:=rezerva[j]; C:=rezerva[k];
    if (A+B<C) or (A+C<B) or (B+C<A) then verificare:=false;
end;


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 do
        for j:=i+1 to n do
         for k:=j+1 to n do
         begin
              if verificare(i,j,k) then inc(m);
         end;
      write(output,m);
      close(input);
      close(output);
End.