A,B = map(int, input().split())
S = list(input())
if A+B+1-len(S) != 0:
    print("No")
    exit()
for i in range(len(S)):
    if (ord(S[i]) < ord("0") or ord(S[i]) > ord("9")) ^ i == A:
        print("No")
        exit()
print("Yes")
