#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1'000'000;
const int INF = 1'000'000'000;
int n, a[N + 10], b[N + 10];
int dp[N + 10], x[N + 10];
int c[N + 10][4][2];
void readInput() {
cin >> n;
for (int i = 1; i <= n; i++) {
char c;
cin >> c;
a[i] = (c == '1');
}
for (int i = 1; i <= n; i++) {
char c;
cin >> c;
b[i] = (c == '1');
}
n++;
a[n] = 1;
b[n] = 1;
}
int check(int i, int t, int j, int add = 0) {
if (add + j == 2)
return c[i][t][j] - 1;
return c[i][t][j] - (add + j == 1 && t == 2);
}
void calcDP(int i) {
if (a[i] != b[i]) {
dp[i] = INF;
return;
}
if (i == 1) {
dp[i] = 0;
return;
}
dp[i] = min(dp[i - 1], x[i - 1]);
for (int t = 1; t <= 3; t++)
for (int j = 0; j <= 1; j++)
dp[i] = min(dp[i], check(i - 1, t, j));
}
void calcX(int i) {
if (a[i] == b[i]) {
x[i] = INF;
return;
}
if (i == 1) {
x[i] = 1;
return;
}
x[i] = min(x[i - 1], dp[i - 1] + 1);
for (int t = 1; t <= 3; t++)
for (int j = 0; j <= 1; j++)
x[i] = min(x[i], check(i - 1, t, j, 1) + 1);
}
void calcC1(int i) {
if (i == 1) {
c[i][1][0] = 1;
c[i][1][1] = INF;
return;
}
c[i][1][0] = dp[i - 1] + 1;
c[i][1][1] = x[i - 1] + 1;
if (b[i] == b[i - 1]) {
c[i][1][0] = min(c[i][1][0], c[i - 1][1][0]);
c[i][1][1] = min(c[i][1][1], c[i - 1][1][1]);
}
}
void calcC23(int i) {
if (i == 1) {
for (int t = 2; t <= 3; t++)
c[i][t][0] = c[i][t][1] = INF;
return;
}
if (b[i] == b[i - 1]) {
for (int t = 2; t <= 3; t++) {
c[i][t][0] = c[i - 1][t][0];
c[i][t][1] = c[i - 1][t][1];
}
}
else {
for (int j = 0; j <= 1; j++) {
c[i][2][j] = min(c[i - 1][1][j], c[i - 1][3][j]) + 1;
c[i][3][j] = c[i - 1][2][j];
}
}
}
void calcAns() {
for (int i = 1; i <= n; i++) {
calcDP(i);
calcX(i);
calcC1(i);
calcC23(i);
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
readInput();
calcAns();
cout << dp[n] << flush;
return 0;
}
