#include <bits/stdc++.h>

using namespace std;
using ll = long long;

constexpr int N = 16;

int pos[N][3], cost[N][N], nxt[N][2];
int dp[N], dq[N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    memset(pos, -1, sizeof(pos));

    for (int t = 0; t < 2; ++t) {
        array<int, 3> p{0, 1, 2};

        for (int i = 6 * t; i < 6 * (t + 1); ++i) {
            nxt[i][1] = 1;
            for (int k = 0; k < 3 - t; ++k) {
                pos[i][p[k]] = k;
                if (p[k] == 0) {
                    nxt[i][0] = nxt[i][1] = 0;
                } else if (p[k] == 1) {
                    nxt[i][0] = nxt[i][1] = 1;
                } else {
                    nxt[i][0] ^= 1, nxt[i][1] ^= 1;
                }
            }
            next_permutation(p.begin(), p.end());
        }
    }

    pos[12][0] = 0, pos[13][1] = 0, pos[14][2] = 0;
    nxt[12][0] = nxt[12][1] = 0;
    nxt[13][0] = nxt[13][1] = 1;
    nxt[14][0] = 1, nxt[14][1] = 0;
    nxt[15][0] = 0, nxt[15][1] = 1;

    for (int x = 0; x < N; ++x) {
        for (int y = 0; y < N; ++y) {
            int siz = y < 6 ? 3 : y < 12 ? 2 : y < 15 ? 1 : 0;

            if (x == y) {
                cost[x][y] = 0;
                continue;
            } else if (x == 15) {
                cost[x][y] = siz;
                continue;
            } else if (y == 15) {
                cost[x][y] = 0;
                continue;
            }

            bool yay = false;
            bool same = false;

            for (int a = 0; a < 3; ++a) {
                for (int b = a + 1; b < 3; ++b) {
                    if (pos[x][a] != -1 && pos[x][b] != -1 && pos[y][a] != -1 && pos[y][b] != -1) {
                        if ((pos[x][a] < pos[x][b]) == (pos[y][a] < pos[y][b])) {
                            yay = true;
                        }
                    }
                }
                if (pos[x][a] != -1 && pos[y][a] != -1) {
                    same = true;
                }
            }

            if (yay) {
                cost[x][y] = siz - 2;
            } else {
                cost[x][y] = siz - same;
            }
        }
    }

    int n;
    cin >> n;

    vector<int> A(n), B(n);
    string sa, sb;
    cin >> sa >> sb;

    for (int i = 0; i < n; ++i) {
        A[i] = sa[i] - '0';
    }
    for (int i = 0; i < n; ++i) {
        B[i] = sb[i] - '0';
    }

    fill(dp, dp + N, 1e9);
    dp[15] = 0;

    for (int i = 0; i < n; ++i) {
        copy(dp, dp + N, dq);
        fill(dp, dp + N, 1e9);

        for (int x = 0; x < N; ++x) {
            if (nxt[x][A[i]] == B[i]) {
                for (int y = 0; y < N; ++y) {
                    dp[x] = min(dp[x], dq[y] + cost[y][x]);
                }
            }
        }
    }

    int ans = *min_element(dp, dp + N);

    cout << ans << '\n';

    return 0;
}