#include<stdio.h>
#define N 100009
#include<set>
#define IT std::set < node > :: iterator
#include<iostream>
#define cin std::cin 

struct node
{
	int l, r;
	mutable char val;
	node(int L, int R = -1, char VAL = 0) : l(L), r(R), val(VAL){}
	inline bool operator < (const node& a)const
	{
		return l < a.l;
	}
};

std::set < node > s;

inline IT split(int pos)
{
	IT it = s.lower_bound(node(pos));
	if (it != s.end() && it -> l == pos)
		return it;
	it --;
	int l = it -> l, r = it -> r;
	char val = it -> val;
	s.erase(it);
	s.insert(node(l, pos - 1, val));
	return s.insert(node(pos, r, val)).first;
}

inline void bulldoze(int l, int r, char val)
{
	IT itr = split(r + 1), itl = split(l);
	s.erase(itl, itr);
	s.insert(node(l, r, val));
}

inline int query(int l, int r, char val)
{
	IT itr = split(r + 1), itl = split(l);
	int ret = 0;
	while (itl != itr)
	{
		if (itl -> val == val)
			ret += (itl -> r - itl -> l + 1);
		itl ++;
	} 
	return ret;
}

inline void Sort(int l, int r)
{
	int cnt[39];
	for (int i = 0;i < 28;i ++)
		cnt[i] = 0;
	IT itr = split(r + 1), itl = split(l), tmp = itl;
	while (itl != itr)
		cnt[itl -> val - 'A'] += itl -> r - itl -> l + 1, itl ++;
	s.erase(tmp, itr);
	int cur = l;
	for(int i = 0;i < 26;i ++)
		if (cnt[i])
			s.insert(node(cur, cur + cnt[i] - 1, i + 'A')), cur += cnt[i];
}

int main()
{
	int n, m;
	scanf("%d%d", &n, &m);
	char ch;
	for (int i = 1;i <= n;i ++)
	{
		cin >> ch;
		if (ch >= 'a')
			ch = ch - 'a' + 'A';
		s.insert(node(i, i, ch));
	} 
	int opt, l, r;
	while (m --)
	{
		scanf("%d%d%d", &opt, &l, &r);
		if (opt != 3)
		{
			cin >> ch;
			if (ch >= 'a')
				ch = ch - 'a' + 'A';
		}
		if (opt == 1)
			printf("%d\n", query(l, r, ch));
		if (opt == 2)
			bulldoze(l, r, ch);
		if (opt == 3)
			Sort(l, r);
	}
	
	return 0;
}