var nr5,p,nr2:longint;
ok:boolean;
i,j:integer;
f,g:text;
begin
assign(f,'fact.in');
reset(f);
assign(g,'fact.out');
rewrite(g);
read(f,p);
i:=1;
while not ok do begin
     j:=i;
     while j mod 5=0 do begin
           j:=j div 5;
           inc(nr5);
           end;
     while j mod 2=0 do begin
           j:=j div 2;
           inc(nr2);
           end;
     if nr2>nr5 then if nr5=p then ok:=true;
     if nr5>=nr2 then if nr2=p then ok:=true;
     inc(i);
     end;
write(g,i-1);
close(f);
close(g);
end.