print((function (f)
	return f(io.stdin:read("*l"):match("%d+%s(%d+)"), io.stdin:read("*l"))
end)(function (i, s)
	local n = 0
	if s:sub(i,i) == "(" then
		for j=i,#s do
			n = s:sub(j,j) == "(" and n+1 or n-1
			if n == 0 then return j end
		end
	else
		for j=i,1,-1 do
			n = s:sub(j,j) ~= "(" and n+1 or n-1
			if n == 0 then return j end
		end
	end
end))