#include<bits/stdc++.h>
#define int long long
using namespace std;
char val[200001];
int tmp[31];
struct Tree{
	int l;
	int r;
	int lazy;
	int num[31];
}tree[800001];
void pushup(int k)
{
	for(int i = 1;i <= 26;++ i)
	{
		tree[k].num[i] = tree[k << 1].num[i] + tree[k << 1 | 1].num[i];
	}
	return;
}
void pushdown(int k)
{
	tree[k << 1].lazy = tree[k].lazy;
	tree[k << 1 | 1].lazy = tree[k].lazy;
	memset(tree[k << 1].num , 0 , sizeof tree[k << 1].num);
	memset(tree[k << 1 | 1].num , 0 , sizeof tree[k << 1 | 1].num);
	tree[k << 1].num[tree[k].lazy] = tree[k << 1].r - tree[k << 1].l + 1;
	tree[k << 1 | 1].num[tree[k].lazy] = tree[k << 1 | 1].r - tree[k << 1 | 1].l + 1;
	tree[k].lazy = 0;
	return;
}
void build(int l , int r , int k)
{
	tree[k].l = l;
	tree[k].r = r;
	tree[k].lazy = 0;
	memset(tree[k].num , 0 , sizeof tree[k].num);
	if(l == r)
	{
		++ tree[k].num[val[l] - 'a' + 1];
		return;
	} 
	int mid = l + (r - l) / 2;
	build(l , mid , k << 1);
	build(mid + 1 , r , k << 1 | 1);
	pushup(k);
	return;
}
int query(int l , int r , int k , int c)
{
	if(l <= tree[k].l && tree[k].r <= r)
	{
		return tree[k].num[c];
	}
	if(tree[k].lazy != 0)
		pushdown(k);
	int mid = tree[k].l + (tree[k].r - tree[k].l) / 2 , res = 0;
	if(l <= mid)
	{
		res += query(l , r , k << 1 , c);
	}
	if(r > mid)
	{
		res += query(l , r , k << 1 | 1 , c);
	}
	return res;
}
void change(int l , int r , int k , int c)
{
	if(l <= tree[k].l && tree[k].r <= r)
	{
		memset(tree[k].num , 0 , sizeof tree[k].num);
		tree[k].num[c] = tree[k].r - tree[k].l + 1;
		tree[k].lazy = c;
		return;
	}
	if(tree[k].lazy != 0)
		pushdown(k);
	int mid = tree[k].l + (tree[k].r - tree[k].l) / 2;
	if(l <= mid)
	{
		change(l , r , k << 1 , c);
	}
	if(r > mid)
	{
		change(l , r , k << 1 | 1 , c);
	}
	pushup(k);
	return; 
}
void query_sort(int l , int r)
{
	memset(tmp , 0 , sizeof tmp);
	for(int i = 1;i <= 26;++ i)
	{
		tmp[i] = query(l , r , 1 , i);
	}
	int last = 0;
	for(int i = 1;i <= 26;++ i)
	{
		if(tmp[i] == 0)
		{
			continue;
		}
		change(last + 1 , last + tmp[i], 1 , i);
		last = last + tmp[i];
	}
	return;
}
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	int n = 0,m = 0;
	cin >> n >> m;
	for(int i = 1;i <= n;++ i)
	{
		char tmp;
		cin >> tmp;
		if(tmp >= 'A' && tmp <= 'Z')
		{
			tmp += 32;
		}
		val[i] = tmp;
	}
	build(1 , n , 1);
	for(int i = 1;i <= m;++ i)
	{
		int opt = 0 , x = 0 , y = 0;
		char k;
		cin >> opt;
		switch (opt)
		{
			case 1:{
				cin >> x >> y;
				cin >> k;
				if(k >= 'A' && k <= 'Z')
				{
					k += 32;
				}
				cout << query(x , y , 1 , k - 'a' + 1) << endl;
				break;
			} 
			case 2:{
				cin >> x >> y;
				cin >> k;
				if(k >= 'A' && k <= 'Z')
				{
					k += 32;
				}
				change(x , y , 1 , k - 'a' + 1);
				break;
			} 
			default:{
				cin >> x >> y;
				query_sort(x , y);
				break;
			}
		}
	}
	return 0;
 }