#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd_init() char*rp=({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define rep(v,e) for(typeof(e)v=0;v<e;++v)
#define repeat(e) for(typeof(e)_=e;_--;)

typedef unsigned long ulong;

ulong b2[26];
ulong b1[26][1<<6];
ulong b0[26][1<<12];

void bsadd(int c,int x){
	b2[c]|=1ul<<(x>>12);
	b1[c][x>>12]|=1ul<<(x>>6);
	b0[c][x>>6]|=1ul<<x;
}

void bsdel(int c,int x){
	if(!(b0[c][x>>6]&=~(1ul<<x))){
		if(!(b1[c][x>>12]&=~(1ul<<(x>>6)))){
			b2[c]&=~(1ul<<(x>>12));
		}
	}
}

int bsminge(int c,int x){
	{
		ulong a=b0[c][x>>6]&~0ul<<x;
		if(a){
			int i=__builtin_ctzl(a)|x&~0x3ful;
			return i;
		}
	}
	x=(x|0x3f)+1;
	{
		ulong a=b1[c][x>>12]&~0ul<<(x>>6);
		if(a){
			int j=__builtin_ctzl(a)|x>>6&~0x3ful;
			int i=__builtin_ctzl(b0[c][j])|j<<6;
			return i;
		}
	}
	x=(x|0xfff)+1;
	{
		ulong a=b2[c]&~0ul<<(x>>12);
		if(a){
			int k=__builtin_ctzl(a);
			int j=__builtin_ctzl(b1[c][k])|k<<6;
			int i=__builtin_ctzl(b0[c][j])|j<<6;
			return i;
		}
	}
	return -1;
}

char wbuf[1<<25];
char s[200000];

int main(){
	char*wp=wbuf;
	rd_init();
	int n=rd();
	int q=rd();
	rep(i,n){
		s[i]=*rp++-'a';
		bsadd(s[i],i);
	}
	++rp;
	repeat(q){
		int t=*rp; rp+=2;
		if(t=='1'){
			int i=rd()-1;
			bsdel(s[i],i);
			s[i]=*rp-'a'; rp+=2;
			bsadd(s[i],i);
		}else{
			int j=-1;
			for(int c;c=*rp++-'a',c>=0;){
				j=bsminge(c,j+1);
				if(j<0){
					while(*rp++-'a'>=0){
					}
					*wp++='N';
					*wp++='o';
					goto hoge;
				}
			}
			*wp++='Y';
			*wp++='e';
			*wp++='s';
			hoge:;
			*wp++='\n';
		}
	}
	write(1,wbuf,wp-wbuf);
	_exit(0);
}