#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

template<class Val>
struct BinaryIndexedTree {
    int n;
    vector<Val> t;
    BinaryIndexedTree() {}
    BinaryIndexedTree(int _n) :n(_n + 1), t(_n + 1) {}
    void add(int k, Val val) {
        k++;
        while (k < n) {
            t[k] += val;
            k += (k&-k);
        }
    }
    void set(int k, Val val) {
        add(k, -sum(k, k + 1));
        add(k, val);
    }
    Val sum(int k) {
        Val r = 0;
        while (k > 0) {
            r += t[k];
            k -= (k&-k);
        }
        return r;
    }
    Val sum(int l, int r) {
        return sum(r) - sum(l);
    }
};

int N;
int f(vector<pii> a) {
    BinaryIndexedTree<int> bit(N);

    sort(all(a));

    int re = 0;
    each(p, a) {
        re += bit.sum(p.second, N);
        bit.add(p.second, 1);
    }
    return re;
}

void solve() {
    
    cin >> N;

    vector<pii> le, ri, riri;
    rep(i, N) {
        int to;
        cin >> to;
        --to;
        if (i <= to) {
            le.emplace_back(i, to);
        } else {
            ri.emplace_back(i, to);
            riri.emplace_back(N - 1 - i, N - 1 - to);
        }
    }

    int ans = 0;
    each(l, le) {
        each(r, ri) {
            if (l.first <= r.first && l.second >= r.second) {
                ans++;
            }
        }
    }

    ans += f(le) + f(riri);
    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}