#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;
for(int i = 0; i < n; ++i) {
for(int j = i + 1; j < n; ++j) {
int hi = h[i];
int hj = h[j];
int di = j - i;
// solve for k, and check
// 1) hi=di, hj=dj, hk=dk
if (hi == di) {
int dj = hj; // so dj = H[j]
int k = j + dj; // k = j + (k-j)
if (k < N && k > j && H[k] == di + dj)
ans++;
}
// 2) hi=di, hj=dk, hk=dj
if (hi == di) {
// hj = dk = di + dj => dj = hj - di
int dj = hj - di;
int k = j + dj;
if (dj > 0 && k < N && k > j && H[k] == dj)
ans++;
}
// 3) hi=dj, hj=di, hk=dk
if (hj == di) {
int dj = hi;
int k = j + dj;
if (k < N && k > j && H[k] == di + dj)
ans++;
}
// 4) hi=dj, hj=dk, hk=di
// hi = dj
// hj = dk = di + dj
if (hj == di + hi) {
int dj = hi;
int k = j + dj;
if (k < N && k > j && H[k] == di)
ans++;
}
// 5) hi=dk, hj=di, hk=dj
// hi = dk = di + dj => dj = hi - di
if (hj == di) {
int dj = hi - di;
int k = j + dj;
if (dj > 0 && k < N && k > j && H[k] == dj)
ans++;
}
// 6) hi=dk, hj=dj, hk=di
// hi = di + dj => dj = hi - di
// hj = dj => hj == hi - di
if (hj == hi - di) {
int dj = hi - di;
int k = j + dj;
if (dj > 0 && k < N && k > j && H[k] == di)
ans++;
}
}
}
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({4, 1, 4, 3, 2, 6, 1});
return 0;
}*/
