#include <stdio.h>
int main(){
    //input
    int n;
    char S[1001];
    char T[1001];
    scanf("%d",&n);
    scanf("%s",S);
    scanf("%s",T);

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

    //output
    printf("%d\n",count);
    return 0;
}