import sys
import math
import itertools
import collections
import heapq
import re
import numpy as np
from functools import reduce

rr = lambda: sys.stdin.readline().rstrip()
rs = lambda: sys.stdin.readline().split()
ri = lambda: int(sys.stdin.readline())
rm = lambda: map(int, sys.stdin.readline().split())
rl = lambda: list(map(int, sys.stdin.readline().split()))
inf = float('inf')
mod = 10**9 + 7

a, b = rm()
s = rr()
for i in range(a):
    if int(s[i]) not in range(10):
        print('No')
        exit()
for i in range(b):
    if int(s[a+1+i]) not in range(10):
        print('No')
        exit()
print('Yes')












