// clang-format off #include using namespace std; #define int long long #define stoi stoll using pii = pair; using vi = vector; using vvi = vector; #define all(c) begin(c), end(c) #define rall(c) rbegin(c), rend(c) #define fore(x, c) for(auto &&x : c) #define rep(i, a, n) for(int i = a, i##len = (int)(n); i < i##len; ++i) #define rrep(i, a, n) for(int i = (int)(n - 1); i >= a; --i) #define sz(c) ((int)c.size()) #define contains(c, x) (c.find(x) != end(c)) #define inseg(l, x, r) ((l) <= (x) && (x) < (r)) #define dump(...) #define pb push_back #define eb emplace_back #define _ 0 const signed INF_ = 1001001001; const long long INF = 1001001001001001001LL; const int DX[9] = {0,1,0,-1,1,1,-1,-1,0}, DY[9] = {-1,0,1,0,-1,1,1,-1,0}; template ostream& operator<<(ostream &os, const vector &v) { for (auto i = begin(v); i != end(v); i++) os<<*i<<(i==end(v)-1?"":" ");return os;} template istream& operator>>(istream &is, vector &v) { for (auto i = begin(v); i != end(v); i++) is>>*i;return is;} template istream& operator>>(istream &is, pair &p) { is>>p.first>>p.second;return is;} template bool chmax(T &a, const U &b){return a bool chmin(T &a, const U &b){return a>b?a=b,1:0;} template void psum(T& c) {partial_sum(begin(c), end(c), begin(c));} template using heap = priority_queue, greater>; struct before_main_function { before_main_function() { cin.tie(nullptr); ios::sync_with_stdio(0); cout << setprecision(15) << fixed; } } before_main_function; // clang-format on //------------------8<------------------------------------8<-------------------- signed main() { int N; cin >> N; vi B(N); cin >> B; int ans = 0; int idx = 0; rep(i, 0, N) { while (B[i]) { ans += abs(i - idx); idx++; B[i]--; } } cout << ans << endl; return (0 ^ _ ^ 0); }