#include <bits/stdc++.h>
#define eb emplace_back
#define printv(a, b) { \
for(auto pv : a) b << pv << " "; \
b << "\n"; \
}
using namespace std;
int gettype(vector<int>& now){
int n = now.size();
int diff = 0;
for(int i = 0; i < n; i++){
if(now[i] == 1) diff++;
}
if(diff == 0) return 3;
else if(diff == n) return 2;
int l = 0, r = 0;
for(int i = 0; i < n && now[i] == 1; i++) l++;
for(int i = n - 1; i >= 0 && now[i] == 1; i--) r++;
if(l + r != diff) return 4;
if(r == 0) return 5;
if(l == 0) return 6;
return 1;
}
vector<int> v, l, r;
vector<bool> del;
bool check(int id){
if(del[id]) return false;
if(v[id] != 1) return false;
if(l[id] != -1 && del[l[id]]) return false;
if(r[id] != -1 && del[r[id]]) return false;
return !(l[id] != -1 && v[l[id]] != 3 && v[l[id]] != 5 && r[id] != -1 && v[r[id]] != 3 && v[r[id]] != 6);
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n;
string a, b;
cin >> n >> a >> b;
a += ' ';
b += ' ';
vector<int> now;
char lst = 0;
int ans = 0;
for(int i = 0; i <= n; i++){
if(i != 0 && b[i] != lst && !now.empty()){
int t = gettype(now);
now.clear();
if(t == 4) ans++;
else v.eb(t);
}
lst = b[i];
now.eb(a[i] != b[i]);
}
int m = v.size();
del.resize(m);
l.resize(m, -1);
r.resize(m, -1);
for(int i = 0; i < m; i++){
if(i) l[i] = i - 1;
if(i < m - 1) r[i] = i + 1;
}
queue<int> q;
for(int i = 0; i < m; i++){
if(check(i)){
q.push(i);
del[i] = true;
}
}
while(!q.empty()){
int now = q.front();
q.pop();
ans++;
if(l[now] != -1) r[l[now]] = r[now];
if(r[now] != -1) l[r[now]] = l[now];
if(l[now] != -1 && check(l[now])){
del[l[now]] = true;
q.push(l[now]);
}
if(r[now] != -1 && check(r[now])){
del[r[now]] = true;
q.push(r[now]);
}
}
//printv(v, cerr);
//printv(del, cerr);
bool tmp = false;
for(int i = 0; i < m; i++){
if(del[i]) continue;
if(v[i] == 1){
ans++;
tmp = true;
}
if(v[i] == 2){
tmp = true;
}
if(v[i] == 3){
if(tmp) ans++;
tmp = false;
}
if(v[i] == 5){
ans++;
tmp = false;
}
if(v[i] == 6){
if(tmp) ans++;
tmp = true;
}
}
if(tmp) ans++;
cout << ans << "\n";
return 0;
}
