#include<bits/stdc++.h>
using namespace std;
int n,cnt,res;
string s1,s2;
int main()
{
	cin>>n>>s1>>s2;
	s1+=" ",s2+=" ";
	for(int i=0;i<=n;i++)
	{
		if(s1[i]!=s2[i])
		{
			cnt++;
		}
		else
		{
			if(cnt)
			{
				res++;
			}
			cnt=0;
		}
	}
	cout<<res;
	return 0;
}