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

using ll = int_fast64_t;
#define rep(i,n) for(int i=0;i<int(n);++i)
#define repr(i,n) for(int i{n};i-->0;)

signed main(){

  int n;
  cin>>n;
  vector<ll> a(n);
  for(auto& ai:a)cin>>ai;

  auto solve = [](int n,auto a)->bool{
    int plus = 0;
    for(int i=n;i-->0;){
      if(a[i]==0)continue;
      if(a[i]+plus!=i+1)return false;
      plus++;
    }
    return true;
  };
  cout<<(solve(n,a)?"Yes":"No")<<endl;

}