#include <iostream>

int main(void)
{
  int n, count=0;
  char s[1000];
  char t[1000];
  scanf("%d", &n);
  scanf("%s", s);
  scanf("%s", t);
  for (int i = 0; i < n; i++)
  {
    if (s[i]!=t[i])
    {
      count += 1;
    }
  }
  printf("%d\n", count);
}