#include "bits/stdc++.h"
#define MOD 1000000007
#define INF 11234567890
#define in std::cin
#define out std::cout
#define rep(i,N) for(LL i=0;i<N;++i)
typedef long long int LL;

int n;
std::string S, T;
int ans;

int main()
{
	in >> n >> S >> T;

	rep(i, n)
	{
		if (S[i] != T[i])
		{
			++ans;
		}
	}

	out << ans << std::endl;
	return 0;
}