var i,aux5,p,aux:longint;
    f:text;
begin
assign(f,'fact.in');
reset(f);
read(f,p);
close(f);
if p=0 then begin
            assign(f,'fact.out');
            rewrite(f);
            write(f,1);
            close(f);
            halt;
            end
else if p=1 then begin
                 assign(f,'fact.out');
                 rewrite(f);
                 write(f,5);
                 close(f);
                 halt;
                 end
else begin
     i:=0;
     aux5:=0;
     while  (aux5<p)
           begin
           inc(i);
           aux:=i;
           while aux mod 5=0 do begin
                              aux:=aux div 5;
                              inc(aux5);
                              end;
           if (aux5=p)  then begin
                             assign(f,'fact.out');
                             rewrite(f);
                             write(f,i);
                             close(f);
                             halt;
                             end;
           end;
     end;
     assign(f,'fact.out');
     rewrite(f);
     write(f,-1);
     close(f);
     end.