import sys
import math



def search(lst, x):
    l, h = 0, len(lst) - 1
    while l <= h:
        m = (l + h) // 2
        if lst[m] == x:
            return True
        elif lst[m] < x:
            l = m + 1
        else:
            h = m - 1
    return False


def isSub(s1, s2):
    n = len(s1)
    m = len(s2)
    i, j = 0, 0
    while i < n and j < m:
        if s1[i] == s2[j]:
            i += 1
            j += 1
        else:
            i += 1
    return j == m

for _ in range(1):
    s1 = str(input())
    s2 = str(input())
    lst1 = []
    lst2 = []
    for i in s1:
        lst1.append(i)
    for i in s2:
        lst2.append(i)
    v = list(map(int, input().split()))
    n = len(s1)
    l, h = 0, n
    ans = -1

    while l <= h:
        m = (l + h) // 2
        lstx = lst1[:]
        for i in range(m):
            lstx[v[i] - 1] = '.'
        if isSub(lstx, lst2):
            ans = m
            l = m + 1
        else:
            h = m - 1
    print(ans)