#include<bits/stdc++.h>
#include "doll.h"
#define pb push_back
using namespace std;
const int maxn = 3e5 + 5;
int n , m , sz;
int nTime = 1;
int a[maxn] , b[maxn];
void build(int x , int l , int r , int sz){
int mid = l + r >> 1;
if(l + 1 == r){
if(sz <= mid)a[x] = 1;
return;
}
b[x] = ++nTime;
build(b[x] , l , mid , sz);
if(sz > mid){
a[x] = ++nTime;
build(a[x] , mid + 1 , r , sz);
}else{
a[x] = 1;
}
}
bool vis[maxn];
void dfs(int u , int val){
vis[u] ^= 1;
int & res = (vis[u] ? a[u] : b[u]);
if(res)dfs(res , val);
else res = val;
}
void create_circuit(int M, std::vector<int> A) {
A.pb(0);
int p = 1;
while(p * 2 <= (int)A.size() - 2)p <<= 1;
build(1 , 1 , p * 2 , (int)A.size() - 1);
for(int i = 1 ; i < A.size() ; ++i)dfs(1 , -A[i]);
vector<int> X(nTime) , Y(nTime) , C(M + 1 , -1);
C[0] = A[0];
for(int i = 0 ; i < nTime ; ++i)X[i] = -a[i + 1] , Y[i] = -b[i + 1];
answer(C, X, Y);
}
#ifdef LOCAL
#include <cstdio>
#include <cstdlib>
#include "doll.h"
namespace {
constexpr int P_MAX = 20000000;
constexpr int S_MAX = 400000;
int M, N;
std::vector<int> A;
bool answered;
int S;
std::vector<int> IC, IX, IY;
int read_int() {
int x;
if (scanf("%d", &x) != 1) {
fprintf(stderr, "Error while reading input\n");
exit(1);
}
return x;
}
void wrong_answer(const char *MSG) {
printf("Wrong Answer: %s\n", MSG);
exit(0);
}
void simulate() {
if (S > S_MAX) {
char str[50];
sprintf(str, "over %d switches", S_MAX);
wrong_answer(str);
}
for (int i = 0; i <= M; ++i) {
if (!(-S <= IC[i] && IC[i] <= M)) {
wrong_answer("wrong serial number");
}
}
for (int j = 1; j <= S; ++j) {
if (!(-S <= IX[j - 1] && IX[j - 1] <= M)) {
wrong_answer("wrong serial number");
}
if (!(-S <= IY[j - 1] && IY[j - 1] <= M)) {
wrong_answer("wrong serial number");
}
}
int P = 0;
std::vector<bool> state(S + 1, false);
int pos = IC[0];
int k = 0;
FILE *file_log = fopen("log.txt", "w");
fprintf(file_log, "0\n");
for (;;) {
fprintf(file_log, "%d\n", pos);
if (pos < 0) {
if (++P > P_MAX) {
fclose(file_log);
char str[50];
sprintf(str, "over %d inversions", P_MAX);
wrong_answer(str);
}
state[-pos] = !state[-pos];
pos = state[-pos] ? IX[-(1 + pos)] : IY[-(1 + pos)];
} else {
if (pos == 0) {
break;
}
if (k >= N) {
fclose(file_log);
wrong_answer("wrong motion");
}
if (pos != A[k++]) {
fclose(file_log);
wrong_answer("wrong motion");
}
pos = IC[pos];
}
}
fclose(file_log);
if (k != N) {
wrong_answer("wrong motion");
}
for (int j = 1; j <= S; ++j) {
if (state[j]) {
wrong_answer("state 'Y'");
}
}
printf("Accepted: %d %d\n", S, P);
}
} // namespace
void answer(std::vector<int> C, std::vector<int> X, std::vector<int> Y) {
if (answered) {
wrong_answer("answered not exactly once");
}
answered = true;
// check if input format is correct
if ((int)C.size() != M + 1) {
wrong_answer("wrong array length");
}
if (X.size() != Y.size()) {
wrong_answer("wrong array length");
}
S = X.size();
IC = C;
IX = X;
IY = Y;
}
int main() {
M = read_int();
N = read_int();
A.resize(N);
for (int k = 0; k < N; ++k) {
A[k] = read_int();
}
answered = false;
create_circuit(M, A);
if (!answered) {
wrong_answer("answered not exactly once");
}
FILE *file_out = fopen("out.txt", "w");
fprintf(file_out, "%d\n", S);
for (int i = 0; i <= M; ++i) {
fprintf(file_out, "%d\n", IC[i]);
}
for (int j = 1; j <= S; ++j) {
fprintf(file_out, "%d %d\n", IX[j - 1], IY[j - 1]);
}
fclose(file_out);
simulate();
return 0;
}
#endif // LOCAL
