#include <bits/stdc++.h>
using namespace std;
typedef int ll;
const ll maxn = 200005;
map<ll,vector<ll>> b;
long long count_triples(std::vector<int> a) {
ll ans = 0;
ll N = a.size();
// i,k,j
for(int i=0;i<N;i++){
ll j = i+a[i];
if(j>=N || a[j]>=a[i]) continue;
ll k = j-a[j];
ans += (a[k]+a[j]==a[i]);
//equidistant
if(2*a[j]==a[i]) continue;
k = i+a[j];
ans += (a[k]+a[j]==a[i]);
}
for(int j=0;j<N;j++){
ll i = j-a[j];
if(i<0 || a[i]>=a[j]) continue;
ll k = i+a[i];
ans += (a[k]+a[i]==a[j]);
//equidistant
if(2*a[i]==a[j]) continue;
k = j-a[i];
ans += (a[k]+a[i]==a[j]);
}
for(int i=0;i<N;i++){
ll j = i+a[i];
if(j>=N || a[j]<=a[i]) continue;
ll k = i+a[j];
if(k>=N || a[k]==a[i]) continue;
ans += (a[k]+a[i]==a[j]);
}
//h[i] = k-j
//h[k] = j-i
//h[j] = k-i
//h[i]-h[j] = i-j
//h[i]-i = h[j]-j
//h[k]+h[j] = j+k
//h[k]-k = h[j]-j
for(int i=0;i<N;i++) b[a[i]-i].push_back(i);
ll cutoff = sqrt(N);
for(pair<ll,vector<ll>> itr:b){
ll x = itr.first;
vector<ll> vec = itr.second;
if(vec.size()<=cutoff){
for(int i:vec) for(int j:vec){
if(i==j) continue;
ll k = i+a[j];
if(j<k && k<N){
ans += (a[i]==k-j && a[j]==(k-i) && a[k]==(i-j));
}
}
}
else{
for(int k=0;k<N;k++){
//k-x = h[k]+2i
ll lhs = k-x;
ll rhs = a[k];//2i
if(lhs%2==rhs%2){
ll i = (lhs-rhs)/2;
ll j = (lhs+rhs)/2;
ans += (0<=i && i<N && 0<=j && j<N && a[i]-i==x && a[j]-j==x);
}
}
}
}
return ans;
}
std::vector<int> construct_range(int M, int K) {
vector<int> res; res.push_back(1);
for (int i = 1; i < M; i ++) res.push_back(i);
return res;
}
/*void run_part1() {
int N;
assert(1 == scanf("%d", &N));
std::vector<int> H(N);
for (int i = 0; i < N; i++)
assert(1 == scanf("%d", &H[i]));
fclose(stdin);
long long T = count_triples(H);
printf("%lld\n", T);
fclose(stdout);
}
void run_part2() {
int M, K;
assert(2 == scanf("%d %d", &M, &K));
fclose(stdin);
std::vector<int> H = construct_range(M, K);
int N = H.size();
printf("%d\n", N);
for (int i = 0; i < N; i++)
printf("%d%c", H[i], " \n"[i + 1 == N]);
fclose(stdout);
}
int main() {
int part;
assert(1 == scanf("%d", &part));
if (part == 1)
run_part1();
else if (part == 2)
run_part2();
return 0;
}*/
