#include <bits/stdc++.h>
#include "sorting.h"
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
#define block_of_code if(true)
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
struct DSU{
int n;
vector<int> parent, sz;
vector<pair<int, int>> history;
DSU(int _n){
n = _n;
parent.resize(n); sz.resize(n, 1);
for(int i = 0; i<n; ++i) parent[i] = i;
}
int find_set(int u){return (u == parent[u]) ? u : find_set(parent[u]);}
bool same_set(int u, int v){return find_set(u) == find_set(v);}
bool join_set(int u, int v){
u = find_set(u), v = find_set(v);
if (u != v){
if (sz[u] < sz[v]) swap(u, v);
parent[v] = u;
sz[u] += sz[v];
history.push_back({u, v});
return true;
}
return false;
}
int get_size(int u){return sz[find_set(u)];}
int get_version(){return history.size();}
void roll_back(int version){
while(get_version() > version){
int u, v;
tie(u, v) = history.back(); history.pop_back();
parent[v] = v;
sz[u] -= sz[v];
}
}
};
const int N = 2e5 + 69;
vector<pair<int, int>> st[N * 4];
int R;
void update(int u, int v, pair<int, int> val, int l, int r, int id){
if (val.first == val.second) return;
if (u <= l && r <= v){
st[id].push_back(val);
return;
}
int mid = (l + r) >> 1;
if (u <= mid) update(u, v, val, l, mid, id * 2);
if (v > mid) update(u, v, val, mid + 1, r, id * 2 + 1);
}
void traverse(int l, int r, int id, DSU &mst){
int cur = mst.get_version();
for(pair<int, int> i: st[id]) mst.join_set(i.first, i.second);
if (l == r){
if (mst.get_version() <= l) R = l;
mst.roll_back(cur);
return;
}
int mid = (l + r) >> 1;
if (R == -1) traverse(l, mid, id * 2, mst);
if (R == -1) traverse(mid + 1, r, id * 2 + 1, mst);
mst.roll_back(cur);
}
int findSwapPairs(int n, int a[], int m, int x[], int y[], int p[], int q[]) {
R = -1;
minimize(m, n);
vector<int> perm(n);
for(int i = 0; i < n; ++i) perm[i] = a[i];
for(int i = 0; i<=m*4+4; ++i) st[i].clear();
vector<int> mp(n, 0);
for(int i = 1; i<=m; ++i){
int u = x[i-1], v = y[i-1];
if (u == v) continue;
update(mp[u], i-1, {u, perm[u]}, 0, m, 1);
update(mp[v], i-1, {v, perm[v]}, 0, m, 1);
mp[u] = mp[v] = -1;
swap(perm[u], perm[v]);
mp[u] = mp[v] = i;
}
for(int i = 0; i < n; ++i) if (mp[i] != -1){
update(mp[i], m, {i, perm[i]}, 0, m, 1);
}
DSU mst(n);
mst.history.reserve(n);
traverse(0, m, 1, mst);
for(int i = 0; i < n; ++i) perm[i] = a[i];
for(int i = 0; i < R; ++i) swap(perm[x[i]], perm[y[i]]);
vector<bool> visited(n);
vector<pair<int,int>> swaps;
for(int i = 0; i<n; ++i) if (!visited[i]) {
int u = i;
while(!visited[u]){
visited[u] = true;
if (!visited[perm[u]]) swaps.push_back({u, perm[u]});
u = perm[u];
}
}
reverse(ALL(swaps));
vector<int> pos(n);
for(int i = 0; i<n; ++i) perm[i] = a[i];
for(int i = 0; i<n; ++i) pos[perm[i]] = i;
for(int i = 0; i < R; ++i){
int u = x[i], v = y[i];
swap(perm[u], perm[v]);
swap(pos[perm[u]], pos[perm[v]]);
if (swaps.size()){
u = pos[swaps.back().first], v = pos[swaps.back().second];
swaps.pop_back();
}
else u = v = 0;
swap(perm[u], perm[v]);
swap(pos[perm[u]], pos[perm[v]]);
p[i] = u, q[i] = v;
}
return R;
}
// int main(void){
// ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// clock_t start = clock();
// int n; cin >> n;
// int a[n];
// for(int i = 0; i<n; ++i) cin >> a[i];
// int m; cin >> m;
// int x[m], y[m];
// for(int i = 0; i<m; ++i) cin >> x[i] >> y[i];
// int p[m], q[m];
// memset(p, -1, sizeof p); memset(q, -1, sizeof q);
// int r = findSwapPairs(n, a, m, x, y, p, q);
// cout << r << "\n";
// for(int i = 0; i < r; ++i) {
// swap(a[x[i]], a[y[i]]);
// swap(a[p[i]], a[q[i]]);
// cout << p[i] << " " << q[i] << "\n";
// }
// for(int i = 0; i < n; ++i) cout << a[i] << " "; cout << "\n";
// cerr << "Time elapsed: " << clock() - start << " ms\n";
// return 0;
// }
/*
5
4 3 2 1 0
6
0 1
1 2
2 3
3 4
0 1
1 2
*/
