#include <stdio.h>
#include <stdlib.h>

int main(void){
    int n, i, count = 0;
    char *S, *T;

    scanf("%d\n", &n);
    S = (char*)calloc(n+2, sizeof(char));
    T = (char*)calloc(n+2, sizeof(char));
    fgets(S, n+2, stdin);
    fgets(T, n+2, stdin);
    for(i=0; *(S+i); i++) if(*(S+i)-*(T+i)) count++;
    printf("%d\n", count);

    free(S);
    free(T);
    return 0;
}