var  f,g:text;
     k,i,n1,n2,nr,p,j:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
i:=0;j:=0;k:=0;
repeat
inc(i);n1:=i;n2:=i;
repeat
if n1 mod 2=0 then
                begin
                inc(j);
                n1:=n1 div 2;
                end;
until n1 mod 2<>0;
repeat
if n2 mod 5=0 then
                begin
                inc(k);
                n2:=n2 div 5;
                end;
until (n2 mod 5<>0) or (k=nr);
if k<=j then nr:=k
        else nr:=j;
until nr=p;
writeln(g,i);
close(f);
close(g);
end.