#include <bits/stdc++.h>
using namespace std;
#define def auto
inline int chic(char c)
{
	return ((c >= 'A' && c <= 'Z') ? c - 'A' : c - 'a');
}
struct ODT
{
	int l, r;
	mutable int v;
	ODT(const int &il, const int &ir, const int &iv):
		l(il), r(ir), v(iv)
	{
	}
	inline bool operator<(const ODT&o) const
	{
		return l < o.l;
	}
};
inline bool cmp(const ODT a, const ODT b)
{
	return a.v < b.v;
}
set<ODT> odt;
int n, m, bucket[27];
inline def split(int x)
{
	if (x > n)
	{
		return odt.end();
	}
	auto it = --odt.upper_bound(ODT(x, 0, 0));
	if(it->l == x)
	{
		return it;
	}
	int l = it->l, r = it->r, v = it->v;
	odt.erase(it);
	odt.insert(ODT(l, x - 1, v));
	return odt.insert(ODT(x, r, v)).first;
}
inline int count(int l, int r, int k)
{
	auto itr = split(r + 1), itl = split(l);
	int ans = 0;
	for(; itl != itr; ++itl)
	{
		if(itl->v == k)
		{
			ans += itl->r - itl->l + 1;
		}
	}
	return ans;
}
inline void assign(int l, int r, int v)
{
	auto itr = split(r + 1), itl = split(l);
	odt.erase(itl, itr);
	odt.insert(ODT(l, r, v));
}
inline void sort(int l, int r)
{
	auto itr = split(r + 1), itl = split(l);
	int cur = l, i;
	memset(bucket, 0, sizeof bucket);
	for(; itl != itr; itl++)
	{
		bucket[itl->v] += itl->r - itl-> l + 1;
		odt.erase(itl);
	}
	for(i = 0; i <= 25; i++)
	{
		if(bucket[i] != 0)
		{
			odt.insert(ODT(cur, cur + bucket[i], i));
			cur += bucket[i] + 1;
		}
	}
}
int main()
{
	int i, ltc, l = 1, opt, x, y;
	char tc, k;
	cin>>n>>m;
	cin>>tc;
	ltc = chic(tc);
	for(i = 2; i <= n; i++)
	{
		cin>>tc;
		if(ltc != chic(tc))
		{
			odt.insert(ODT(l, i - 1, ltc));
			ltc = chic(tc);	
			l = i;
		}
	}
	odt.insert(ODT(l, n, chic(tc)));
	while(m--)
	{
		cin>>opt>>x>>y;
		switch(opt)
		{
		case 1:
			{
				cin>>k;
				cout<<count(x, y, chic(k))<<endl;
				break;
			}
		case 2:
			{
				cin>>k;
				assign(x, y, chic(k));
				break;
			}
		case 3:
			{
				sort(x, y);
				break;
			}
		}
	}
	return 0;
}