647 B | 647 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
BLANK = " "
inp = input
# inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def f(s):
n = len(s)
ret = ""
for i in range(n // 2):
cnt = int(s[2 * i])
crt = s[2 * i + 1]
ret += crt * cnt
return ret
def solve():
k, pos = mii()
s = input()
for _ in range(k):
s = f(s)
p(s[pos])
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()