a,b=map(int,input().split())
c=input()
f={}
for i in range(a):
	if c[i] in f:
		f[c[i]].add(i)
	else:
		f[c[i]]=set([i])
for i in range(b):
	d=list(map(str,input().split()))
	if len(d)==2:
		if d[1][0] not in f or f[d[1][0]]==set():
			print('No')
			continue
		n=True
		for j in f[d[1][0]]:
			if j+len(d[1])<=a and c[j:j+len(d[1])]==d[1]:
				print('Yes')
				n=False
				break
		if n:
			print('No')
	else:
		f[c[int(d[1])-1]].remove(int(d[1])-1)
		if d[2] in f:
			f[d[2]].add(int(d[1])-1)
		else:
			f[d[2]]=set([int(d[1])-1])
		e=list(c)
		e[int(d[1])-1]=d[2]
		c="".join(e)