#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <stack>
using namespace std;

#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
#define SQR(X) ((X)*(X))

typedef long long ll;
typedef unsigned long long ull;
typedef long double lb;
/* ここからが本編 */

int main(void)
{
   int i,j;
   int n;
   char s[1005];
   char c;
   int cnt = 0;
   cin >> n;
   cin >> s;
   for(i=0;cin >> c;i++) {
      if(c != s[i]) cnt++;
   }
   cout << cnt << endl;
   return 0;
}