#include <bits/stdc++.h>
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define ALL(v) (v).begin(), (v).end()
#define LLA(v) (v).rbegin(), (v).rend()
#define PB push_back
#define MP(a, b) make_pair((a), (b))
using namespace std;
template <class T> inline vector<T> make_vec(size_t a, T val) {
    return vector<T>(a, val);
}
template <class... Ts> inline auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec(ts...))>(a, make_vec(ts...));
}
template <typename T> inline T read() {
    T t;
    cin >> t;
    return t;
}
template <typename T> inline vector<T> readv(size_t sz) {
    vector<T> ret(sz);
    rep(i, sz) cin >> ret[i];
    return ret;
}
template <typename... Ts> inline tuple<Ts...> reads() {
    return {read<Ts>()...};
}
template <typename T> struct edge {
    int to;
    T cost;
    edge(int t, T c) : to(t), cost(c) {}
};
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using Graph = vector<vector<int>>;
template <typename T> using WGraph = vector<vector<edge<T>>>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N = read<int>();
    auto B = readv<int>(N);
    vector<int> zero, ball;
    rep(i, N) {
        if(B[i] == 0) {
            zero.push_back(i);
        }
        if(B[i] > 1) {
            for(int j = 0; j < B[i] - 1; j++)
                ball.push_back(i);
        }
    }
    ll res = 0;
    rep(i, zero.size()) { res += abs(zero[i] - ball[i]); }
    cout << res << endl;
}