#include <bits/stdc++.h>
using namespace std;

#define int long long
#define double long double

#define pii pair<int, int>

signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
#ifdef CB
	freopen("be2.txt", "r", stdin);
//	freopen("out.txt", "w", stdout);
#endif
	int N;
	cin >> N;
	vector<int> v(N);
	for (int i = 0; i < N; i++) {
		cin >> v[i];
	}
	map<int, int> m;
	int ans = 0;
	for (int i = 0; i < N; i++) {
		v[i] = (v[i] + ans) % N;
		if (!m.count(v[i])) {
			auto t = m.insert({v[i], ans}).first;
			if (t != m.begin() && t->first - t->second <= prev(t)->first - prev(t)->second) {
				t = m.erase(t);
			}
		}
		auto t = m.upper_bound(i);
		int d = 0;
		if (t == m.begin()) {
			d = max(0ll, N + i - m.rbegin()->first - (ans - m.rbegin()->second));
		}
		else {
			d = max(0ll, i - prev(t)->first - (ans - prev(t)->second));
		}
		if (i) d = min(d, 1ll);
		ans += d;
	}
	cout << ans << '\n';
	return 0;
}