#include<stdio.h>
main(){
    int N;
    char S[1001],T[1001];
    scanf("%d",&N);
    scanf("%s %s",S,T);
    int count = 0;
    for(int i = 0;i < N;i++){
        if(S[i] != T[i]){count++;}
    }
    printf("%d",count);
}