579 B | 579 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n = ii()
s = inp()
idx = 0
crt = 1
while idx < len(s):
crt_s = str(crt)
if crt_s != s[idx: idx + len(crt_s)]:
p(crt_s)
break
idx += len(crt_s)
crt += 1
else:
p(n)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
d = solve()