var i,p,n,m,k,x,y,s:longint;
    f:text;
begin
assign(f,'magazin.in');
reset(f);
readln(f,p,n,m,k);
for i:=1 to n do
  begin
  readln(f,x,y);
  s:=s+y;
  end;
close(f);
s:=s+n*k+6;
assign(f,'magazin.out');
rewrite(f);
writeln(f,s);
close(f);
end.