#include<bits/stdc++.h>
using namespace std;
using ll = long long;
int len;
int s, t;
const int N = (1 << 19);
int get_num(string s) {
int res = 0;
for(int i = (int)s.size() - 1, pw = 1; i >= 0; i--, pw *= 2) {
if(s[i] == '1') res += pw;
}
return res;
}
vector<int> g1, g2;
int dist[N];
vector<bool> vis(N);
int main() {
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin >> len;
string s0, t0;
cin >> s0 >> t0;
if(len <= 18) {
s = get_num(s0), t = get_num(t0);
for(int i = 0; i < len; i++) {
int x = 0;
for(int j = i; j < len; j++) {
x |= (1 << j);
g1.push_back(x);
g2.push_back((((1 << len) - 1) ^ x));
}
}
queue<int> q;
q.push(s);
vis[s] = 1;
while(!q.empty()) {
int cur = q.front();
if(cur == t) break;
q.pop();
for(int c : g1) {
int to = (cur | c);
if(!vis[to]) q.push(to), dist[to] = dist[cur] + 1, vis[to] = 1;
to = (cur ^ c);
if(!vis[to]) q.push(to), dist[to] = dist[cur] + 1, vis[to] = 1;
}
for(int c : g2) {
int to = (cur & c);
if(!vis[to]) q.push(to), dist[to] = dist[cur] + 1, vis[to] = 1;
}
}
cout << dist[t];
return 0;
}
if(s0 == string(len, '0')) {
int ans = 0;
for(int i = 0; i < len - 1; i++)
ans += (t0[i] != t0[0] && t0[i + 1] == t0[0]);
ans += (t0[len - 1] != t0[0]);
cout << ans;
}
}
