var f,g:text;
    n,p,prod,c2,c5,copie:longint;
begin
 assign(f,'fact.in');reset(f);
 assign(g,'fact.out');rewrite(g);
 readln(f,p);
 n:=0;
 c2:=0;
 c5:=0;
 repeat
       n:=n+1;
       copie:=n;
       while (copie mod 2=0) and (c2<p) do begin
             c2:=c2+1;
             copie:=copie div 2;
       end;
       while (copie mod 5=0) and (c5<p) do begin
             c5:=c5+1;
             copie:=copie div 5;
       end;
 until ((c2=p)and(c5>=c2)) or ((c5=p)and(c2>=c5));
 write(g,n);
 close(f);
 close(g);
end.