#include <bits/stdc++.h>

using namespace std;

#define ll long long

int a[];

struct node

{

    int num;

    int x;

}s[];

bool cmp(node a,node b)

{

    return a.x<b.x;

}

int main()

{

    int i,j,n;

    cin>>n;

    for(i=;i<=n;i++){

        cin>>s[i].x;

        s[i].num=i;

    }

    sort(s+,s+n+,cmp);

    int now=;

    for(i=;i<=n;i++){

        a[s[i].x]=s[i].num;

        for(j=;j<s[i].num;j++){

            while(a[now]) now++;

            a[now]=s[i].num;

        }

        if(now>s[i].x) {cout<<"No"<<endl;return ;}

    }

    for(i=;i<=n;i++){

        for(j=;j<=n-s[i].num;j++){

            while(a[now]) now++;

            if(now<s[i].x) {cout<<"No"<<endl;return ;}

            a[now]=s[i].num;

        }

    }

    cout<<"Yes"<<endl;

    return ;

}