#include<bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
#define pb push_back
#define pii pair<int, int>
#define pll pair<ll, ll>
#define st first
#define nd second
#define ordered_set tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>
#define debug false
const int MAXN = 1000 * 1000 + 17;
string a, b;
int dp[MAXN][4];
int st[MAXN * 4];
void aktualizuj(int p, int k, int ind, ll w, int i) {
if (p == k && p == ind) {
st[i] = w;
return;
}
int sr = (p + k) / 2;
if (ind <= sr) {
aktualizuj(p, sr, ind, w, i * 2);
} else {
aktualizuj(sr + 1, k, ind, w, i * 2 + 1);
}
st[i] = min(st[i * 2], st[i * 2 + 1]);
}
int zapytanie(int p, int k, int a, int b, int i) {
if (p > b || k < a) {
return MAXN;
}
if (a <= p && k <= b) {
return st[i];
}
int sr = (p + k) / 2;
return min(zapytanie(p, sr, a, b, i * 2), zapytanie(sr + 1, k, a, b, i * 2 + 1));
}
int main () {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n;
cin >> n >> a >> b;
a = "#" + a;
b = "#" + b;
for (int i = 1; i <= n; i ++) {
if (b[i] == '1') {
dp[i][1] = dp[i - 1][1] + 1;
}
if (b[i] == '0') {
dp[i][0] = dp[i - 1][0] + 1;
}
if (a[i] == b[i]) {
dp[i][2] = dp[i - 1][2] + 1;
}
if (a[i] != b[i]) {
dp[i][3] = dp[i - 1][3] + 1;
}
}
for (int i = 1; i <= n; i ++) {
int x = MAXN;
if (dp[i][0] != 0) {
x = min(x, zapytanie(0, n, i - dp[i][0], i - 1, 1) + 1);
}
if (dp[i][1] != 0) {
x = min(x, zapytanie(0, n, i - dp[i][1], i - 1, 1) + 1);
}
if (dp[i][2] != 0) {
x = min(x, zapytanie(0, n, i - dp[i][2], i - 1, 1));
}
if (dp[i][3] != 0) {
x = min(x, zapytanie(0, n, i - dp[i][3], i - 1, 1) + 1);
}
aktualizuj(0, n, i, x, 1);
}
cout << zapytanie(0, n, n, n, 1) << "\n";
return 0;
}
