#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
typedef long long ll;

int N;
int A[200000];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    cin >> N;
    for(int i = 0; i < N; i++) cin >> A[i];
    int cnt = 0;
    for(int i = N-1; i >= 1; i--){
        if(A[i]+cnt == 0) continue;
        if(A[i]+cnt != i+1){
            cout << "No" << endl;
            return 0;
        }
        cnt++;
    }
    cout << "Yes" << endl;
}