var f,g:text;
        p,a,b,i,nr,d,nr1,c:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
if p=0 then write(g,1);
a:=p;
b:=p;
for i:= 1 to maxlongint do begin
        if i mod 2=0 then begin
                        c:=i div 2;
                        nr:=nr+1;
                        end;
        if (nr>=a)and(nr1>=b) then break;
        if i mod 5=0 then begin
                        d:=i mod 5;
                        nr1:=nr1+1;
                        end;
        if (nr>=a)and(nr1>=b) then break;
        end;
write(g,i);
close(f);
close(g);
end.