var k,i,nr,p,n:longint;  f,g:text;
begin
assign(f,'fact.in');reset(f);read(f,p);close(f);assign(g,'fact.out');rewrite(g);
i:=2;
k:=1;
if p=0 then write(1)
else
begin
repeat
k:=k*i;
if (k>9)and(k mod 10=0) then begin inc(nr); k:=k div 10 end;
inc(i); k:=k mod 10;
until nr=p ;
writeln(g,i);
close(g);
end
end.