C - Rails

#include<cstdio>
#include<stack>
#include<cstring>
using namespace std;
int a[1010];
int main()
{
	int n;
	while (~scanf("%d",&n) && n)
	{
		while (1)
		{
			stack<int> s;
			scanf("%d",&a[0]);
			if (!a[0]) 
			{
				puts("");
				break;
			}
			for (int i = 1;i < n;i ++)
				scanf("%d",&a[i]);
			int pos = 0;
			for (int i = 1;i <= n;i ++)
			{
				s.push(i);
				while (!s.empty() && s.top() == a[pos])
				{
					s.pop();
					pos ++;
				}
			}
			if (s.empty()) puts("Yes");
			else puts("No");
		}
		
	}
	return 0;
}