var
   n , s , i : longint;
   a : array [1..100000000] of word;
   f , g : text;
begin

 assign(f,'koba.in');
 reset(f);

 assign(g,'koba.out');
 rewrite(g);

 read(f,n);
 read(f,a[1]);
 read(f,a[2]);
 read(f,a[3]);

 for i:=4 to n do
  a[i]:=a[i-1]+(a[i-2]*a[i-3]);

 s:=0;
 for i:=1 to n do
  s:=s+(a[i]mod 10);

 writeln(g,s);

 close(f);

 close(g);

end.