a,b=map(int,input().split())
c=list(input())
for i in range(b):
	d=list(map(str,input().split()))
	if len(d)==2:
		if list(d[1]) in c:
			print('Yes')
		else:
			print('No')
	else:
		c[int(d[1])-1]=d[2]