#include "bits/stdc++.h"
#pragma GCC optimize("Ofast")

// Begin {{{
using namespace std;

#ifndef DEBUG
#define dump(...)
#endif

template <class A, class B> inline bool chmax(A &a, const B &b) { return b > a && (a = b, true); }
template <class A, class B> inline bool chmin(A &a, const B &b) { return b < a && (a = b, true); }

template <class T>
inline vector<T> make_v(const T &initvalue, size_t sz) {
    return vector<T>(sz, initvalue);
}

template <class T, class... Args>
inline auto make_v(const T &initvalue, size_t sz, Args... args) {
    return vector<decltype(make_v<T>(initvalue, args...))>(sz, make_v<T>(initvalue, args...));
}

constexpr int INF = 0x3f3f3f3f;
constexpr int64_t LINF = 0x3f3f3f3f3f3f3f3fLL;
// }}} End

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    size_t N; cin >> N;

    vector<pair<intmax_t, intmax_t>> exist;
    vector<intmax_t> empty_idx;
    for (size_t i = 0; i < N; ++i) {
        intmax_t b; cin >> b;
        if (b == 0) {
            empty_idx.emplace_back(i);
        } else if (b >= 2) {
            exist.emplace_back(i, b - 1);
        }
    }

    size_t pos = 0;
    intmax_t res = 0;
    for (size_t i = 0; i < exist.size(); ++i) {
        while (exist[i].second--) {
            res += llabs(exist[i].first - empty_idx[pos]);
            pos++;
        }
    }

    cout << res << "\n";

    return 0;
}