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#include <iostream>

using namespace std;

int getBitCount(int k) {
    int count = 0;
    while (k) {
        count += k & 1;
        k >>= 1;
    }

    return count;
}

int edge[100][2];

int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int k;
    cin >> k;

    if (k == 1) {
        cout << 2 << endl;
        cout << "2 -1" << endl;
        cout << "-1 -1" << endl;
        return 0;
    }

    int m = 1;
    int n = 0;
    int lg = 0;
    while (2 * m <= k) {
        m *= 2;
        n += 2;
        lg++;
    }

    int bits = getBitCount(k);
    n += bits;

    int nn = n;
    edge[nn][0] = -1;
    edge[nn][1] = -1;
    for (int i = 0; i < lg; i++) {
        nn--;
        edge[nn][0] = nn + 1;
        edge[nn][1] = -1;
        nn--;
        edge[nn][0] = nn + 1;
        edge[nn][1] = nn + 2;
    }

    k -= m;

    int target = nn + 2;
    while (k > 0) {
        m /= 2;
        if (k & m) {
            nn--;
            edge[nn][0] = nn + 1;
            edge[nn][1] = target;
            k -= m;
        }
        target += 2;
    }

    cout << n << endl;
    for (int i = 1; i <= n; i++) {
        cout << edge[i][0] << " " << edge[i][1] << endl;
    }

    return 0;
}