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



int N;
int A[200010];

signed main() {
	cin >> N;
	for (int i = 0; i < N; i++)cin >> A[i];
	for (int i = 0; i < N; i++) {
		if (A[i] > i + 1) {
			cout << "No" << endl; return 0;
		}
	}
	bool ok = false;
	int cnt = 0;
	for (int i = N - 1; i >= 0; i--) {
		if (ok) {
			if (A[i] > i + 1) {
				cout << "No" << endl; return 0;
			}
			else if ((A[i] - i - 1 + cnt) % (i + 1) != 0) {
				cout << "No" << endl; return 0;
			}
			cnt++;
		}
		else {
			if (A[i] != 0) {
				ok = true;
				if (A[i] > i + 1) {
					cout << "No" << endl; return 0;
				}
				else if ((A[i] - i - 1 + cnt) % (i + 1) != 0) {
					cout << "No" << endl; return 0;
				}
				cnt++;
			}
		}
	}
	cout << "Yes" << endl;
	return 0;
}