#include <stdio.h>

void main(void) {
	int charNum = 0;
	scanf("%d",&charNum);
	char strA[10000] = "a";
	char strB[10000] = "b";
	scanf("%s %s",strA,strB);
	int count = 0;
	for(int i = 0 ; i < charNum ; i++){
		if(strA[i] != strB[i]){
			count++;
		}
	}
	printf("%d",count);
}