#include <bits/stdc++.h>
#define all(vec) vec.begin(), vec.end()
using namespace std;
using ll = long long;
using P = pair<int, int>;
constexpr ll INF = (1LL << 30) - 1LL;
constexpr ll LINF = (1LL << 60) - 1LL;
constexpr ll MOD = 1e9 + 7;
template <typename T> void chmin(T &a, T b) { a = min(a, b); }
template <typename T> void chmax(T &a, T b) { a = max(a, b); }
int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    vector<ll> v;
    for (int i = 0; i < n; i++) {
        int b;
        cin >> b;
        for (int j = 0; j < b; j++) {
            v.push_back(i);
        }
    }
    ll res = 0;
    for (int i = 0; i < n; i++) {
        res += abs(v[i] - i);
    }
    cout << res << endl;
}