#include <iostream>
#include <vector>
#include <set>
#include <cassert>

using namespace std;

int main() {
    int n; cin >> n;
    vector<int> c(1+n);
    for (int i = 1; i <= n; ++i) cin >> c[i];
    vector< pair<int, int> > ops; // operations

    vector<bool> seen(1+n);
    for (int i = 1; i <= n; ++i) {
        if (c[i] == i) seen[i] = true;
    }
    int waiting = 0;

    auto swp = [&](int pos1, int pos2) {
        ops.emplace_back(pos1, pos2);
        swap(c[pos1], c[pos2]);
    };

    // fix 2 loops a and b in size_a + size_b operations
    auto pairLoop = [&](int a, int b) {
        swp(a, b);
        while (c[a] != b) swp(a, c[a]);
        while (c[b] != a) swp(b, c[b]);
        swp(a, b);
    };

    for (int i = 1; i <= n; ++i) {
        if (seen[i]) continue;
        int node = i;
        do {
            seen[node] = true;
            node = c[node];
        } while (node != i);
        if (!waiting) waiting = i;
        else {
            pairLoop(i, waiting);
            waiting = 0;
        }
    }

    if (waiting) {
        int inPlace = 0;
        for (int i = 1; i <= n; ++i) {
            if (c[i] == i) {
                inPlace = i;
                break;
            }
        }
        if (inPlace) {
            pairLoop(inPlace, waiting);
        } else { // All nodes in one loop, thus at least 3 nodes
            // cancel 1 loop a in size_a + 1 operations
            assert(c[c[waiting]] != waiting);
            int x = c[waiting];
            swp(waiting, x);
            while (c[c[waiting]] != waiting) swp(waiting, c[waiting]);

            int y = waiting, z = c[waiting]; // x and z are flipped coins, y is not
            swp(x, z);
            swp(y, z);
            swp(x, y);
        }
    }

    for (int i = 1; i <= n; ++i) assert(c[i] == i);
    assert(ops.size() <= n+1);
    cout << ops.size() << endl;
    for (pair<int, int> o : ops) cout << o.first << ' ' << o.second << endl;
    return 0;
}
