#include <bits/stdc++.h>
using namespace std;
#define overload3(_NULL, _1, _2, name, ...) name
#define rep1(i, n) for (remove_const_t<remove_reference_t<decltype(n)>> i = 0; i < (n); i++)
#define rep2(i, a, b) for (remove_const_t<remove_reference_t<decltype(a)>> i = a; i < (b); i++)
#define rep(...) overload3(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)
#if __has_include(<debug.hpp>)
#    include <debug.hpp>
#else
#    define dbg(...) (void(0))
#endif
template<class T> void drop(const T &x) {
    cout << x << "\n";
    exit(0);
}
template<class T> bool chmax(T &a, const T &b) { return a < b and (a = b, true); }
template<class T> bool chmin(T &a, const T &b) { return a > b and (a = b, true); }
using i64 = long long;
using usize = size_t;

int main() {
    int n;
    cin >> n;
    vector<int> p(n);
    for (auto &&pi: p) cin >> pi;
    int ans = n * (n + 1) / 2;
    rep(i, n) if (p[i] == n) ans -= (i + 1) * 2;
    if (p.back() == n and p.size() <= 3) ans = 0;
    cout << ans << "\n";
}

struct IOSetup {
    IOSetup() noexcept {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
        cout << fixed << setprecision(10);
        cerr << fixed << setprecision(10);
    }
} iosetup;