#include <bits/stdc++.h>
using namespace std;
char A[1000005], B[1000005];
int X[1000005][6];
int f(int x, int y) {
return (x / 3 && y / 3 == 0) + (x % 3 != y % 3 && x % 3);
}
int main() {
ios_base::sync_with_stdio(0), cin.tie(0);
int N; cin >> N;
cin >> A + 1 >> B + 1;
for (int i = 0; i <= N; ++i) fill(X[i], X[i] + 6, 1e9);
X[0][0] = 0;
for (int i = 1; i <= N; ++i) {
int t = (A[i] - '0') << 1 | (B[i] - '0');
if (t == 0) {
for (int j = 0; j < 6; ++j) {
X[i][0] = min(X[i][0], X[i - 1][j] + f(0, j));
X[i][1] = min(X[i][1], X[i - 1][j] + f(1, j));
X[i][5] = min(X[i][5], X[i - 1][j] + f(5, j));
}
}
else if (t == 1) {
for (int j = 0; j < 6; ++j) {
X[i][3] = min(X[i][3], X[i - 1][j] + f(3, j));
X[i][4] = min(X[i][4], X[i - 1][j] + f(4, j));
X[i][2] = min(X[i][2], X[i - 1][j] + f(2, j));
}
}
else if (t == 2) {
for (int j = 0; j < 6; ++j) {
X[i][3] = min(X[i][3], X[i - 1][j] + f(3, j));
X[i][1] = min(X[i][1], X[i - 1][j] + f(1, j));
X[i][5] = min(X[i][5], X[i - 1][j] + f(5, j));
}
}
else {
for (int j = 0; j < 6; ++j) {
X[i][0] = min(X[i][0], X[i - 1][j] + f(0, j));
X[i][4] = min(X[i][4], X[i - 1][j] + f(4, j));
X[i][2] = min(X[i][2], X[i - 1][j] + f(2, j));
}
}
}
cout << *min_element(X[N], X[N] + 6);
return 0;
}
