#include <bits/stdc++.h>

[[nodiscard]] static inline constexpr uint_fast32_t solve(const uint_fast32_t n, const std::string& S, const std::string& T) noexcept
{
	uint_fast32_t ans = 0;
	for (uint_fast32_t i = 0; i < n; ++i)
		if (S[i] != T[i]) ++ans;

	return ans;
}

int main()
{
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);
	
	uint_fast32_t n;
	std::string S, T;
	std::cin >> n;
	S.reserve(n), T.reserve(n);
	std::cin >> S >> T;

	std::cout << solve(n, S, T) << '\n';
	return 0;
}