#include <cstdio>
#include <climits>
#include <vector>
#include <algorithm>
#include <queue>
#include <stdio.h>
#include <string>


#define REP(i,n) for(int i=0;i<(int)n;++i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define INF 99999999

using namespace std;

int main() {
    int n;
    char s[1024],t[1024];
    
    scanf("%d",&n);
    scanf("%s",s);
    scanf("%s",t);
    int count = 0;
    for(int i = 0; i < n; i++) {
        if(s[i] != t[i]) count++;
    }
    
    printf("%d\n",count);
    
    
    
    
    
    
    
    
}