#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; }*/