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

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

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

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