#include <bits/stdc++.h>
using namespace std;
using i64 = int_fast64_t;
using ui64 = uint_fast64_t;
#define REP(i, n) for (i64 (i) = 0; (i) < (n); ++(i))
#define FOR(i, a, b) for (i64 (i) = (a); (i) < (b); ++(i))

int N;
i64 res;
vector<int> B;

signed main() {

    cin >> N;
    B.resize(N);
    REP(i, N) cin >> B[i];

    vector<int> v;
    REP(i, N) REP(j, B[i]) v.emplace_back(i);

    REP(i, N) res += abs(i - v[i]);

    cout << res << endl;

}