#include <bits/stdc++.h>
#include "sorting.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define fi first
#define se second
#define mp make_pair
#define fastIO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
const int N = (int)2e5 + 10;
int seq[N];
int n, m;
vector<pii> sw;
int who[N];
int nex[N];
int cac[N];
int cur[N];
int ind[N];
vector<pii> soln;
bool can(int k){
soln.clear();
for(int i = 0 ; i < n; i ++ ){
who[i] = i;
cur[i] = seq[i];
ind[cur[i]] = i;
}
for(int i = 0 ; i < k ; i ++ ){
swap(who[sw[i].fi], who[sw[i].se]);
}
for(int i = 0 ; i < n; i ++ ){
nex[who[i]] = i;
}
for(int i = 0 ; i < n; i ++ ){
cac[nex[i]] = i;
}
int cnt = 0;
int pi, qi;
for(int i = 0 ; i < k; i ++ ){
swap(nex[sw[i].fi], nex[sw[i].se]);
cac[nex[sw[i].fi]] = sw[i].fi;
cac[nex[sw[i].se]] = sw[i].se;
swap(cur[sw[i].fi], cur[sw[i].se]);
ind[cur[sw[i].fi]] = sw[i].fi;
ind[cur[sw[i].se]] = sw[i].se;
while(cnt < n){
if(ind[cnt] == cac[cnt]) cnt ++ ;
else{
break;
}
}
if(cnt == n){
soln.push_back(mp(0, 0));
}
else{
pi = ind[cnt];
qi = cac[cnt];
soln.push_back(mp(pi, qi));
swap(cur[pi], cur[qi]);
ind[cur[pi]] = pi;
ind[cur[qi]] = qi;
}
}
while(cnt < n){
if(ind[cnt] == cac[cnt]) cnt ++ ;
else{
break;
}
}
if(cnt == n)
return true;
else
return false;
}
int findSwapPairs(int _N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
P[0] = 0;
Q[0] = 0;
n = _N;
m = M;
for(int i = 0 ; i < n; i ++ ){
seq[i] = S[i];
}
for(int i = 0 ; i < m ; i ++ ){
sw.push_back(mp(X[i], Y[i]));
}
int l = 0, r = m;
int mid;
while(l < r){
mid = (l + r) / 2;
if(can(mid))
r = mid;
else
l = mid + 1;
}
can(l);
for(int i = 0 ; i < l ; i ++ ){
P[i] = soln[i].fi;
Q[i] = soln[i].se;
}
return l;
}
