POJ1363

#include"cstdio"
#include"cstring"
using namespace std;
const int MAXN=1005;
int a[MAXN];
int N;
int s[MAXN];
int cnt;
int main()
{
    while(scanf("%d",&N)!=EOF&&N)
    {
        while(scanf("%d",&a[1])!=EOF&&a[1]!=0)
        {
            cnt=0;
            for(int i=2;i<=N;i++)
            {
                scanf("%d",&a[i]);
            }    
            int l=1;
            for(int i=1;i<=N;i++)
            {
                s[cnt++]=i;
                while(s[cnt-1]==a[l]&&cnt!=0)
                {
                    cnt--;
                    l++;
                }
                
            }
            if(cnt==0)    printf("Yes\n");
            else         printf("No\n");
        }
        printf("\n");
    }
    
    return 0;
}