#include <bits/stdc++.h>
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
int n;
std::cin >> n;
std::string a, b;
std::cin >> a >> b;
std::vector<int> vis(1 << n);
std::vector<int> ans(1 << n, 1e8);
std::queue<int> q;
int start = std::stoi(a, nullptr, 2);
int end = std::stoi(b, nullptr, 2);
q.push(start);
ans[start] = 0;
while (!q.empty()) {
int x = q.front();
q.pop();
if (vis[x]) {
continue;
}
vis[x] = true;
if (x == end) {
break;
}
for (int i = 0; i < n; ++i) {
for (int j = i; j < n; ++j) {
int mask = (1 << (j + 1)) - (1 << i);
int tar = x ^ (x & mask);
ans[tar] = std::min(ans[tar], ans[x] + 1);
q.push(tar);
tar = x ^ ((~(x & mask)) & mask);
ans[tar] = std::min(ans[tar], ans[x] + 1);
q.push(tar);
tar = x ^ mask;
ans[tar] = std::min(ans[tar], ans[x] + 1);
q.push(tar);
}
}
}
std::cout << ans[end] << '\n';
}
