//@formatter:off #include #define overload4(_1,_2,_3,_4,name,...) name #define rep1(i,n) for (ll i = 0; i < ll(n); ++i) #define rep2(i,s,n) for (ll i = ll(s); i < ll(n); ++i) #define rep3(i,s,n,d) for(ll i = ll(s); i < ll(n); i+=d) #define rep(...) overload4(__VA_ARGS__,rep3,rep2,rep1)(__VA_ARGS__) #define rrep(i,n) for (ll i = ll(n)-1; i >= 0; i--) #define all(a) a.begin(),a.end() #define rall(a) a.rbegin(),a.rend() #define popcount(x) __builtin_popcount(x) #define pb push_back #define eb emplace_back #ifdef __LOCAL #define debug(...) { cout << #__VA_ARGS__; cout << ": "; print(__VA_ARGS__); cout << flush; } #else #define debug(...) void(0) #endif #define INT(...) int __VA_ARGS__;scan(__VA_ARGS__) #define LL(...) ll __VA_ARGS__;scan(__VA_ARGS__) #define STR(...) string __VA_ARGS__;scan(__VA_ARGS__) #define CHR(...) char __VA_ARGS__;scan(__VA_ARGS__) #define DBL(...) double __VA_ARGS__;scan(__VA_ARGS__) #define LD(...) ld __VA_ARGS__;scan(__VA_ARGS__) using namespace std; using ll = long long; using ld = long double; using P = pair; using LP = pair; using vi = vector; using vvi = vector>; using vl = vector; using vvl = vector>; using vd = vector; using vvd = vector>; using vs = vector; using vc = vector; using vvc = vector>; using vb = vector; using vvb = vector>; using vp = vector

; using vvp = vector>; template istream& operator>>(istream &is,pair &p) { return is >> p.first >> p.second; } template ostream& operator<<(ostream &os,const pair &p) { return os<<'{'< istream& operator>>(istream &is,vector &v) { for(T &t:v){is>>t;} return is; } template ostream& operator<<(ostream &os,const vector &v) { os<<'[';rep(i,v.size())os< bool chmin(T& a,T b) {if(a > b){a = b; return true;} return false;} template bool chmax(T& a,T b) {if(a < b){a = b; return true;} return false;} void scan(){} template void scan(Head& head, Tail&... tail){ cin >> head; scan(tail...); } template void print(const T& t){ cout << t << '\n'; } template void print(const Head& head, const Tail&... tail){ cout< void fin(const T&... a) { print(a...); exit(0); } const string yes[] = {"no","yes"}; const string Yes[] = {"No","Yes"}; const string YES[] = {"NO","YES"}; const int inf = 1001001001; const ll linf = 1001001001001001001; //@formatter:on template class BIT { int n; vector val; public: BIT(int n) : n(n), val(n + 1, 0) {} void add(int i, T x = 1) { i++; while (i <= n) { val[i] += x; i += i & -i; } } T sum(int i) { T ret = 0; i++; while (i > 0) { ret += val[i]; i -= i & -i; } return ret; } // [l,r) T sum(int l, int r) { return sum(r - 1) - sum(l - 1); } }; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); INT(n); vi a(n); cin >> a; rep(i, n) a[i]--; if (a[0] > a[1]) { rep(i, n) a[i] = n - 1 - a[i]; } ll ans = 0; { vi sum(n + 1); rep(i, 0, n, 2) sum[a[i] + 1]++; rep(i, n) sum[i + 1] += sum[i]; rep(i, 0, n, 2) { int mn = inf; if (i > 0) chmin(mn, a[i - 1]); if (i < n - 1) chmin(mn, a[i + 1]); ans += sum[mn] - sum[a[i] + 1]; } } { vi sum(n + 1); rep(i, 1, n, 2) sum[a[i] + 1]++; rep(i, n) sum[i + 1] += sum[i]; rep(i, 1, n, 2) { int mx = -1; if (i > 0) chmax(mx, a[i - 1]); if (i < n - 1) chmax(mx, a[i + 1]); ans += sum[a[i]] - sum[mx + 1]; } } { BIT bt(n); vp ls; rep(i, 0, n, 2) { int mn = inf; if (i > 0) chmin(mn, a[i - 1]); if (i < n - 1) chmin(mn, a[i + 1]); ls.eb(mn, a[i]); } sort(all(ls)); auto it = ls.begin(); vp add; rep(i, 1, n, 2) { int mx = -1; if (i > 0) chmax(mx, a[i - 1]); if (i < n - 1) chmax(mx, a[i + 1]); add.eb(a[i], mx); } sort(all(add)); for (auto[f, s] : add) { while (it != ls.end() and it->first <= f) { ans += bt.sum(it->second - 1); it++; } bt.add(s); } } print(ans); }