#include <bits/stdc++.h>
using namespace std;

int main()
{
int i;
int n;
int iCnt;
char S[ 1100 ];
char T[ 1100 ];

	cin >> n;
	cin >> S;
	cin >> T;

	iCnt = 0;
	for( i = 0; i < n; i++ )
	{
		if( S[ i ] != T[ i ] ) iCnt++;
	}

	cout << iCnt << endl;

	return 0;
}