program koba;
var a,b,c,n,t,co,s:longint;
    f,g:text;
begin
assign(f,'koba.in');
reset(f);
assign(g,'koba.out');
rewrite(g);
read(f,n,a,b,c);
a:=a mod 10;
b:=b mod 10;
c:=c mod 10;
if n=1 then write(g,a);
if n=2 then write(g,a+b);
if n=3 then write(g,a+b+c);
if n>3 then
  begin
    s:=a+b+c;
    for co:=1 to n-3 do
      begin
        t:=(c+a*b) mod 10;
        inc(s,t);
        a:=b;
        b:=c;
        c:=t;
      end;
    write(g,s);
  end;
close(f);
close(g);
end.