#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define pb push_back
#define mp make_pair
#define endl '\n'
typedef vector<ll> vl;
typedef long int int32;
typedef unsigned long int uint32;
typedef long long int int64;
typedef unsigned long long int  uint64;
#define all(x) x.begin(), x.end()
inline void solve(){
    ll n;cin >> n;
    vl v(n);
    rep(i,0,n){
        cin >> v[i];
    }
    ll trash;cin >> trash;
    stack<int> st;
    for(int i = 0;i < n;i++){
        while(!st.empty() && (st.top() > v[i])){
            st.pop();
        }
        st.push(v[i]);
    }
    vl pos(1005);
    vl ans;
    while(!st.empty()){
        ans.pb(st.top());
        pos[st.top()] = 1;
        st.pop();
    }
    reverse(all(ans));
    for(ll i = n - 1;i >= 0;i--){
        if(pos[v[i]] == 1){
            continue;
        }
        else ans.pb(v[i]);
    }
    cout << ((is_sorted(all(ans)) ? "yes" : "no"));
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    // cin >> t
    while (t--){
        solve();
        cout<<endl;
    }
    return 0;
}