#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int> > tmp;
vector<int> vec;
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, sz, state=0, ans=0;
cin >> n;
string s, t;
cin >> s >> t;
for (int i=0; i<n; i++)
{
if (i && t[i]!=t[i-1])
{
vec.push_back(state);
state=0;
}
if (state%2==0 && s[i]==t[i])
state++;
else if (state<2 && s[i]!=t[i])
state+=2;
}
vec.push_back(state);
sz=vec.size();
for (int i=0; i<sz; i++)
{
if (vec[i]==1)
{
int sz0=tmp.size(), cnt=0;
for (int j=0; j<sz0; j++)
{
//cout << tmp[j].first << ' ' << tmp[j].second << '\n';
if (tmp[j].first==3 || tmp[j].second==1 || (tmp[j].second==2 && j && j<=sz0-2) || (tmp[j].second==3 && cnt%2==0 && j && j<=sz0-2))
cnt+=tmp[j].second;
else
{
if (!cnt)
ans++;
else
ans+=cnt/2+2;
cnt=0;
}
}
if (cnt)
ans+=cnt/2+1;
tmp.clear();
}
else if (tmp.empty() || vec[i]!=tmp.back().first)
tmp.push_back({vec[i], 1});
else
tmp.back().second++;
}
int sz0=tmp.size(), cnt=0;
for (int j=0; j<sz0; j++)
{
//cout << tmp[j].first << ' ' << tmp[j].second << '\n';
if (tmp[j].first==3 || tmp[j].second==1 || (tmp[j].second==2 && j && j<=sz0-2) || (tmp[j].second==3 && cnt%2==0 && j && j<=sz0-2))
cnt+=tmp[j].second;
else
{
if (!cnt)
ans++;
else
ans+=cnt/2+2;
cnt=0;
}
}
if (cnt)
ans+=cnt/2+1;
cout << ans << '\n';
}
