// Please submit with C++17! It's best to use C++20 or higher version.
// By Koicy (https://koicy.ly)
// rbtree ([email protected])
// Only one ace left.

#include <algorithm>
#include <array>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
#define _CONSOLE 0
// #define EFILE ""

using namespace std;
using tp = long long;
constexpr tp ZERO = 0, ONE = 1, INF32 = -1u >> 2, INF = -1ull >> 2;

template <typename _Type, size_t _Size>
struct mray : array<_Type, _Size + 9> {
  _Type& operator[](size_t index) { return this->at(index); }
};

// Defines

// Constants

// Classes

// Typedeves

// Variables
bool g;
tp n, cnt;

// Arraies
mray<tp, 2000000> a, f;

// Functions
void MIST() {
}

// :/

void STRUGGLING([[maybe_unused]] tp TEST_NUMBER) {
  cin >> n;
  for (tp i = 1; i <= n; ++i) cin >> a[i];
  for (tp i = n; i >= 1; --i) f[i] = f[i + 1] + (a[i] <= i) * (a[i] + f[i + 1]) / i;
  for (tp i = 1; i <= n; ++i) g |= a[i] > i;
  for (tp i = n; i >= 1; --i) g |= a[i] <= i && (a[i] + f[i + 1]) % i;
  cout << f[1] + g << '\n';
}

#include <fstream>

signed main() {
  tp t = 0, _t = 1;
  cin.tie(0)->sync_with_stdio(0);
#if !_CONSOLE
#ifdef _LOCAL
  static ifstream _in("input.txt");
  cin.rdbuf(_in.rdbuf());
#else
#ifdef EFILE
  static ifstream _in(EFILE ".in");
  static ofstream _out(EFILE ".out");
  cin.rdbuf(_in.rdbuf());
  cout.rdbuf(_out.rdbuf());
#endif
#endif
#endif
  // cin >> _t;
  MIST();
  while (t < _t) STRUGGLING(++t);
  return 0;
}

//*/