import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class No224 {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		char[] chrS = br.readLine().toCharArray();
		char[] chrT = br.readLine().toCharArray();
		int ans = 0;
		for(int i=0; i < n; i++){
			if(chrS[i] != chrT[i]) ans++;
		}
		System.out.println(ans);
	}
}