Train2020.pas

var a,u,b: array[1..100] of byte;
    n,max,i: byte;

function gcd(a,b: byte): byte;
begin
    if b=0 then gcd:=a
           else gcd:=gcd(b, a mod b)
end;

function R(k, pred: byte): byte;
var i: byte;
begin
    if k>max
      then begin
             max:=k;
             for i:=2 to max do b[i]:=a[i];
           end;
    for i:=2 to n do
      if (u[i]=0) and ((pred=0) or (gcd(pred, i)>1))
        then begin
               u[i]:=1; a[k+1]:=i;
               R(k+1, i);
               u[i]:=0;
             end;
end;

begin
    read(n); max:=1;
    R(1,0);
    write(1);
    for i:=2 to max do write('-', b[i]);
end.