#include <bits/stdc++.h>
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
const int inf = 1e8;
int n;
std::cin >> n;
std::string a, b;
std::cin >> a >> b;
auto xor_val = [&](int i, int j) {
if (i == n) {
return 0;
}
return (j == 2 ? a[i] - '0' : j) ^ (b[i] - '0');
};
// try all 3^n bit strings:
// dp[position][current character][sum of segments mod 2]
// 0 => 0, 1 => 1, 2 => ?
std::vector dp(n + 1, std::vector(3, std::vector<int>(2)));
for (int i = n; i >= 0; --i) {
for (int j = 0; j < 3; ++j) {
for (int k = 0; k < 2; ++k) {
if (i == n) {
dp[i][j][k] = j == 2 ? 0 : inf;
continue;
}
int cur_xor = xor_val(i, j);
if (j == 0) {
// curr char = 0
// 00, 01, 0?
dp[i][j][k] = std::min(
{dp[i + 1][0][k] + (cur_xor == 1 and xor_val(i + 1, 0) != 1),
dp[i + 1][1][1 - k] + (k == 0) +
(cur_xor == 1 and xor_val(i + 1, 1) != 1),
dp[i + 1][2][0] + (k == 0) +
(cur_xor == 1 and xor_val(i + 1, 2) != 1)});
} else if (j == 1) {
// curr char = 1
// 10, 11, 1?
dp[i][j][k] = std::min(
{dp[i + 1][0][1 - k] + (k == 0) +
(cur_xor == 1 and xor_val(i + 1, 0) != 1),
dp[i + 1][1][k] + (cur_xor == 1 and xor_val(i + 1, 1) != 1),
dp[i + 1][2][0] + (k == 0) +
(cur_xor == 1 and xor_val(i + 1, 2) != 1)});
} else {
// curr char = ?
// ?0, ?1, ??
dp[i][j][k] = std::min(
{dp[i + 1][0][1] + (cur_xor == 1 and xor_val(i + 1, 0) != 1) + 1,
dp[i + 1][1][1] + (cur_xor == 1 and xor_val(i + 1, 1) != 1) + 1,
dp[i + 1][2][0] + (cur_xor == 1 and xor_val(i + 1, 2) != 1)});
}
}
}
}
std::cout << std::min({dp[0][0][1] + 1, dp[0][1][1] + 1, dp[0][2][0]})
<< '\n';
}
