struct N{
	ll aa,ab,ac,ad,bb,bc,bd,cc,cd,dd;
};

N segtree_ph_func(N a,N b){
	N r;
	r.aa=a.aa+b.aa;
	r.ab=min(a.aa+b.ab,a.ab+b.bb);
	r.ac=min(a.aa+b.ac,a.ab+b.bc,a.ac+b.cc);
	r.ad=min(a.aa+b.ad,a.ab+b.bd,a.ac+b.cd,a.ad+b.dd);
	r.bb=a.bb+b.bb;
	r.bc=min(a.bb+b.bc,a.bc+b.cc);
	r.bd=min(a.bb+b.bd,a.bc+b.cd,a.bd+b.dd);
	r.cc=a.cc+b.cc;
	r.cd=min(a.cc+b.cd,a.cd+b.dd);
	r.dd=a.dd+b.dd;
	return r;
}

N leaf[]={
	{0,0,0,0,1,1,1,1,1,1},
	{1,0,0,0,0,0,0,1,1,1},
	{1,1,0,0,1,0,0,0,0,1},
	{1,1,1,0,1,1,0,1,0,0},
};

{
	ll@n,@q;
	segtree_ph<N>t;
	t.malloc(n);
	t.setN(n);
	rep(i,n){
		char@c;
		t[i]=leaf[c-'A'];
	}
	t.build();
	rep(q){
		ll@a;
		if(a==1){
			ll@x--;
			char@c;
			t.change(x,leaf[c-'A']);
		}
		if(a==2){
			ll@l--,@r;
			wt(t.get(l,r).ad);
		}
	}
}