New Year is coming in Line World! In this world, there are *n* cells numbered by integers from 1 to *n*, as a 1 × *n* board. People live in cells. However, it was hard to move between distinct cells, because of the difficulty of escaping the cell. People wanted to meet people who live in other cells.

So, user tncks0121 has made a transportation system to move between these cells, to celebrate the New Year. First, he thought of *n* - 1 positive integers *a*<sub class="lower-index">1</sub>, *a*<sub class="lower-index">2</sub>, ..., *a*<sub class="lower-index">*n* - 1</sub>. For every integer *i* where 1 ≤ *i* ≤ *n* - 1 the condition 1 ≤ *a*<sub class="lower-index">*i*</sub> ≤ *n* - *i* holds. Next, he made *n* - 1 portals, numbered by integers from 1 to *n* - 1. The *i*-th (1 ≤ *i* ≤ *n* - 1) portal connects cell *i* and cell (*i* + *a*<sub class="lower-index">*i*</sub>), and one can travel from cell *i* to cell (*i* + *a*<sub class="lower-index">*i*</sub>) using the *i*-th portal. Unfortunately, one cannot use the portal backwards, which means one cannot move from cell (*i* + *a*<sub class="lower-index">*i*</sub>) to cell *i* using the *i*-th portal. It is easy to see that because of condition 1 ≤ *a*<sub class="lower-index">*i*</sub> ≤ *n* - *i* one can't leave the Line World using portals.

Currently, I am standing at cell 1, and I want to go to cell *t*. However, I don't know whether it is possible to go there. Please determine whether I can go to cell *t* by only using the construted transportation system.
The first line contains two space-separated integers *n* (3 ≤ *n* ≤ 3 × 10<sup class="upper-index">4</sup>) and *t* (2 ≤ *t* ≤ *n*) — the number of cells, and the index of the cell which I want to go to.

The second line contains *n* - 1 space-separated integers *a*<sub class="lower-index">1</sub>, *a*<sub class="lower-index">2</sub>, ..., *a*<sub class="lower-index">*n* - 1</sub> (1 ≤ *a*<sub class="lower-index">*i*</sub> ≤ *n* - *i*). It is guaranteed, that using the given transportation system, one cannot leave the Line World.
n,t=map(int, input().strip().split())
a=input().split()

Upd_a=a[0]
for i in range(0,n-1):
    if Upd_a<=a[i]:
        if i+1==t:
            print("YES")
            break
        elif i+1>t:
            print("NO")
            break
        else:
            Upd_a=a[i]
    else:
        Upd_a=a[i]
