514.cpp

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

int main() {
    stack<int> s;
    queue<int> q;
    queue<int> parent;
    int i, j, k, l, n, t = 0;
    while (scanf("%d", &n) == 1) {
        if (n == 0) break;
        while (scanf("%d", &k)) {
            if (k == 0) break;
            parent.push(k);
            for (i = 2; i <= n; i++) {
                scanf("%d", &k);
                parent.push(k);
            }
            for (i = 1; i <= n; i++) q.push(i);
            int flag = 0;
            while (q.size() != 0 || parent.size() != 0) {
                if (q.front() == parent.front()) {
                    q.pop();
                    parent.pop();
                } else if (s.size() != 0 && s.top() == parent.front()) {
                    s.pop();
                    parent.pop();
                } else if (q.size() == 0 && parent.front() != s.top()) {
                    flag = 1;
                    break;
                } else {
                    s.push(q.front());
                    q.pop();
                }
            }
            if (s.size() == 0 && flag == 0)
                puts("Yes");
            else
                puts("No");
            while (q.size() != 0) q.pop();
            while (s.size() != 0) s.pop();
            while (parent.size() != 0) parent.pop();
        }
        printf("\n");
    }
    return 0;
}