#include <bits/stdc++.h>
int dp[2000][2000];
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int n;
std::cin >> n;
if (n > 500) {
std::string a, b;
std::cin >> a >> b;
int ans = 0;
for (int i = 0; i < n; i++) {
if (b[i] != '1') {
continue;
}
while (i + 1 < n && b[i + 1] == '1') {
i++;
}
ans++;
}
std::cout << ans << "\n";
} else {
std::string a, b;
std::cin >> a >> b;
auto cost = [&](char c, int l, int r) {
int ans = 0;
for (int i = l; i <= r; i++) {
if (c != b[i]) {
while (i + 1 <= r && b[i + 1] != c) {
i++;
}
ans++;
}
}
return ans;
};
auto xorcost = [&](int l, int r) {
int ans = 0;
for (int i = l; i <= r; i++) {
if (a[i] != b[i]) {
while (i + 1 <= r && b[i + 1] != a[i + 1]) {
i++;
}
ans++;
}
}
return ans;
};
memset(dp, -1, sizeof dp);
std::function<int(int, int)> calc = [&](int l, int r) {
if (l == r) {
return int(a[l] != b[l]);
}
int &ret = dp[l][r];
if (~ret) {
return ret;
}
ret = 1000000;
ret = std::min(ret, cost('0', l, r) + bool(std::count(a.begin() + l, a.begin() + r + 1, '1')));
ret = std::min(ret, cost('1', l, r) + bool(std::count(a.begin() + l, a.begin() + r + 1, '0')));
ret = std::min(ret, xorcost(l, r));
for (int i = l; i < r; i++) {
ret = std::min(ret, calc(l, i) + calc(i + 1, r));
}
return ret;
};
std::cout << calc(0, n - 1) << "\n";
}
return 0;
}
