# 2020/06/03
# AtCoder Beginner Contest 084 - B

# Input
a, b = map(int,input().split())
s = input()

# Calc
is_a_dec = str.isdecimal(s[0:a])
is_b_dec = str.isdecimal(s[a+1:len(s)])

if is_a_dec and is_b_dec:
    ans = 'Yes'
else:
    ans = 'No'

# Output
print(ans)
