uva 514

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<stack>

using namespace std;
const int maxn=10010;
const int N=10;

int target[maxn];

int main(){

	int n;
	while(scanf("%d",&n)!=EOF){
		
		stack<int> s;
		
		for(int i=1;i<=n;i++)
		scanf("%d",&target[i]);
		
		int ok=1;
	    int A=1,B=1;
	    while(B<=n){
	    	
	    	if(A==target[B])  {A++,B++;}
			else if(!s.empty()&&s.top()==target[B]) { s.pop(); B++; }	
			else if(A<=n) s.push(A++);
			else { ok=0;break; }
		}
		
		printf("%s\n",ok?"Yes":"No");
	}

	return 0;
}