#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define endl "\n"
#define dbg(x) cout << #x << " = " << (x) << endl;
const long long INF = 1e18;
const int MAXN = 1e6 + 10;
const int MOD = 1e9 + 7;
/*bool match(vector<int> a, vector<int> b){
sort(a.begin(), a.end());
sort(b.begin(), b.end());
for(int i = 0; i < 3; ++i) if(a[i] != b[i]) return false;
return true;
}*/
long long count_triples(vector<int> h) {
int n = h.size();
long long ans = 0;
set<vector<int>> s;
for(int k = 0; k < n; ++k){
int i = k - h[k];
int j1 = k - h[i];
if(i < j1 && j1 < k && h[j1] == j1 - i && s.find({i, j1, k}) == s.end()){
ans++;
//cout<<i<<" "<<j1<<" "<<k<<endl;
s.insert({i, j1, k});
}
int j2 = h[i] + i;
if(i < j2 && j2 < k && h[j2] == k - j2 && s.find({i, j2, k}) == s.end() ) {
ans++;
//cout<<i<<" "<<j2<<" "<<k<<endl;
s.insert({i, j2, k});
}
}
return ans;
}
vector<int> construct_range(int m, int k){
return {};
}
/*int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
//freopen("input.in", "r", stdin);
//freopen("input.out", "w", stdout);
cout<<count_triples({1,1,2,2,3,4,4,5,5,7,7});
return 0;
}*/
