StringQuery_CF

#include<bits/stdc++.h>
using namespace std;
const int MAX_N=(int)1e7+777; /// limit for array size
int n; /// array size
int TREE[2*MAX_N];
string str;

void build() /// build the tree
{
	for(int i=n-1;i>=1;--i)
		TREE[i]=TREE[i<<1]|TREE[(i<<1)|1];
}

void modify(char chr,int p) /// set value at position p
{
	--p,p+=n;
	int code=(chr-'a');
	TREE[p]=(1<<code);
    for(;p>0;p>>=1)
        TREE[p>>1]=TREE[p]|TREE[p^1];
}

int func(int l,int r){
	int ans=0;
	--l,--r,l+=n,r+=n,++r;
	while(l<r)
    {
	    if(l&1)
            ans|=TREE[l++];
		if(r&1)
            ans|=TREE[--r];
		l>>=1,r>>=1;
	}
	return __builtin_popcount(ans);
}

int main()
{
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin>>n>>str;
	for(int i=0;i<n;++i)
        TREE[i+n]=(1<<(str[i]-'a'));
	build();
	int q,a,l,r;
	char chr;
	cin>>q;
	while(q--)
	{
		cin>>a>>l;
		if(a==1)
			cin>>chr,modify(chr,l);
		else
			cin>>r,cout<<func(l,r)<<'\n';
	}
	return 0;
}