#include "sorting.h"
#include <bits/stdc++.h>
#define MAXN 200015
using namespace std;
int bk[MAXN],pos_bk[MAXN],pre[MAXN],pos_pre[MAXN];
int solve(int N,int n,int S[],int P[],int Q[],int X[],int Y[]){
int now=0,cnt_same=0;
for (int i=0;i<N;i++){
bk[i]=i; pos_bk[i]=i;
pre[i]=S[i]; pos_pre[S[i]]=i;
if (pre[i]==i) cnt_same++;
}
for (int i=n-1;i>=0;i--){
swap(bk[X[i]],bk[Y[i]]);
pos_bk[bk[X[i]]]=X[i];
pos_bk[bk[Y[i]]]=Y[i];
}
for (int i=0;i<n;i++){
if (cnt_same==N) return i;
if (pre[X[i]]==X[i]) cnt_same--;
if (pre[Y[i]]==Y[i]) cnt_same--;
swap(pre[X[i]],pre[Y[i]]);
if (pre[X[i]]==X[i]) cnt_same++;
if (pre[Y[i]]==Y[i]) cnt_same++;
pos_pre[pre[X[i]]]=X[i];
pos_pre[pre[Y[i]]]=Y[i];
swap(bk[X[i]],bk[Y[i]]);
pos_bk[bk[X[i]]]=X[i];
pos_bk[bk[Y[i]]]=Y[i];
now=i;
while (now<N&&pos_pre[now]==pos_bk[now])
now++;
if (now>=N) continue;
P[i]=pos_pre[now]; Q[i]=pos_bk[now];
if (pre[P[i]]==P[i]) cnt_same--;
if (pre[Q[i]]==Q[i]) cnt_same--;
swap(pre[pos_pre[now]],pre[pos_bk[now]]);
if (pre[P[i]]==P[i]) cnt_same++;
if (pre[Q[i]]==Q[i]) cnt_same++;
pos_pre[pre[pos_pre[now]]]=pos_pre[now];
pos_pre[pre[pos_bk[now]]]=pos_bk[now];
}
bool flag=1;
for (int i=0;i<N;i++){
if (pre[i]!=i) flag=0;
}
if (flag) return n;
else return 1e9;
}
int solve1(int N,int n,int S[],int P[],int Q[],int X[],int Y[]){
for (int i=0;i<N;i++){
bk[i]=i; pos_bk[i]=i;
pre[i]=S[i]; pos_pre[S[i]]=i;
}
for (int i=n-1;i>=0;i--){
swap(bk[X[i]],bk[Y[i]]);
pos_bk[bk[X[i]]]=X[i];
pos_bk[bk[Y[i]]]=Y[i];
}
int now=0;
for (int i=0;i<n;i++){
bool flag=1;
for (int j=0;j<N;j++){
if (pre[j]!=j){
flag=0;
break;
}
}
if (flag)
return i;
swap(pre[X[i]],pre[Y[i]]);
pos_pre[pre[X[i]]]=X[i];
pos_pre[pre[Y[i]]]=Y[i];
swap(bk[X[i]],bk[Y[i]]);
pos_bk[bk[X[i]]]=X[i];
pos_bk[bk[Y[i]]]=Y[i];
now=i;
while (now<N&&pos_pre[now]==pos_bk[now])
now++;
if (now>=N) continue;
P[i]=pos_pre[now]; Q[i]=pos_bk[now];
swap(pre[pos_pre[now]],pre[pos_bk[now]]);
pos_pre[pre[pos_pre[now]]]=pos_pre[now];
pos_pre[pre[pos_bk[now]]]=pos_bk[now];
}
bool flag=1;
for (int i=0;i<N;i++){
if (pre[i]!=i) flag=0;
}
if (flag) return n;
else return 1e9;
}
int findSwapPairs(int N, int S[], int M, int X[], int Y[], int P[], int Q[]) {
/*
int l=0,r=M;
while (l<r){
int mid=(l+r)>>1;
if (solve(N,mid,S,P,Q,X,Y)<1e8) r=mid;
else l=mid+1;
}
return solve(N,l,S,P,Q,X,Y);
*/
int mn=1e9,pos;
for (int i=0;i<M;i++){
int need=solve1(N,i,S,P,Q,X,Y);
if (need<1e8){
if (mn>need){
mn=need;
pos=i;
}
}
}
return solve1(N,pos,S,P,Q,X,Y);
}
