program koba;
var a,b,c,n,t,co,s:longint;
    f,g:text;
procedure citire;
begin
  read(f,n,a,b,c);
end;
procedure transformare(var a:longint);
begin
a:=a mod 10;
end;

procedure lucru;
begin
t:=(c+a*b) mod 10;
inc(s,t);
a:=b;
b:=c;
c:=t;
inc(co);
end;

begin
assign(f,'koba.in');
reset(f);
assign(g,'koba.out');
rewrite(g);
citire;
inc(co,3);
transformare(a);
transformare(b);
transformare(c);
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;
    while co<n do lucru;
    write(g,s);
  end;
close(f);
close(g);
end.