#include<bits/stdc++.h>
#include<atcoder/lazysegtree>
using namespace std;
using namespace atcoder;
const int inf = 1 << 30;

struct S{
    int ind;
    int min_;
};
using F = int;

S e(){
    return S{-1, inf};
}

S op(S l, S r){
    if(l.min_ <= r.min_) return l;
    else return r;
}

S mapping(F l, S r){
    return S({r.ind, r.min_ + l});
}

F composition(F l, F r){
    return l + r;
}

F id(){
    return 0;
}

void solve(){
    int n, a;
    cin >> n;
    vector<S> A(n);
    for(int i = 0; i < n; i++){
        cin >> a;
        A[i].ind = i;
        A[i].min_ = i + 1 - a;
    }
    lazy_segtree<S, op, e, F, mapping, composition, id> seg(A);
    while(1){
        S tmp = seg.prod(0, n);
        if(tmp.min_ != 0) break;
        seg.apply(0, tmp.ind, -1);
        seg.apply(tmp.ind, tmp.ind + 1, tmp.ind + 1);
    }
    for(int i = 0; i < n; i++){
        if(seg.get(i).min_ != i + 1){
            cout << "No\n";
            return;
        }
    }
    cout << "Yes\n";
    
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t;
    t = 1;
    //cin >> t;
    while(t--) solve();
}