Problem:
Score : 500 points

Problem Statement

You are given a string S of length N consisting of lowercase English letters.

Process Q queries of the following two types:

Type 1: change the i_q-th character of S to c_q. (Do nothing if the i_q-th character is already c_q.)

Type 2: answer the number of different characters occurring in the substring of S between the l_q-th and r_q-th characters (inclusive).

Constraints

N, Q, i_q, l_q, and r_q are integers.

S is a string consisting of lowercase English letters.

c_q is a lowercase English letter.

1 \leq N \leq 500000

1 \leq Q \leq 20000

|S| = N

1 \leq i_q \leq N

1 \leq l_q \leq r_q \leq N

There is at least one query of type 2 in each testcase.

Input

Input is given from Standard Input in the following format:

N
S
Q
Query_1
\vdots
Query_Q

Here, Query_i in the 4-th through (Q+3)-th lines is one of the following:

1 i_q c_q

2 l_q r_q

Output

For each query of type 2, print a line containing the answer.

Sample Input 1

7
abcdbbd
6
2 3 6
1 5 z
2 1 1
1 4 a
1 7 d
2 1 7

Sample Output 1

3
1
5

In the first query, cdbb contains three kinds of letters: b , c , and d, so we print 3.

In the second query, S is modified to abcdzbd.

In the third query, a contains one kind of letter: a, so we print 1.

In the fourth query, S is modified to abcazbd.

In the fifth query, S does not change and is still abcazbd.

In the sixth query, abcazbd contains five kinds of letters: a, b, c, d, and z, so we print 5.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for (ll i = a; i < b; i++)
#define REP(i,b) FOR(i,0,b)
#define RFOR(i,a,b) for (ll i = a-1; i >= b; i--)
#define RREP(i,a) RFOR(i,a,0)
#define REPALL(i,x) for (ll i = 0; i < x.size(); i++)
#define RREPALL(i,x) for (ll i = x.size()-1; i >= 0; i--)
#define REPITR(itr,x) for (auto itr = (x).begin(); itr != (x).end(); itr++)
#define ALL(x) (x).begin(), (x).end()
#define SORT(x) sort(ALL(x))
#define MIN_ELEMENT(x) min_element(ALL(x))
#define MAX_ELEMENT(x) max_element(ALL(x))
#define COUNT(x,num) count(ALL(x), num)
#define MEMSET(x,val) memset(x, val, sizeof(x))
#define MAX(a,b) a = max(a,b)
#define MIN(a,b) a = min(a,b)
#define debug(x) cerr<<__LINE__<<": "<<(#x)<<" = "<<(x)<<endl;
void YES(bool flag) {cout<<(flag ? "YES" : "NO")<<endl;}
void Yes(bool flag) {cout<<(flag ? "Yes" : "No")<<endl;}
void yes(bool flag) {cout<<(flag ? "yes" : "no")<<endl;}
#define e1 first
#define e2 second
#define nextline putchar('\n')
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;
typedef vector<ll> VLL;
typedef vector<vector<ll>> VVLL;
const int INF = 1e7;
const ll MOD = 1e9 + 7;

int n, q_num;
string s;
map<char, set<int>> mp;

int main()
{
    cin>>n>>s>>q_num;
    REPALL(k,s) {
        mp[s[k]].insert(k);
    }
    REP(k,q_num) {
        int q;
        cin>>q;
        if (q == 1) {
            int i;
            char c;
            cin>>i>>c;
            mp[s[i-1]].erase(i-1);
            mp[c].insert(i-1);
            s[i-1] = c;
            //debug(s);
        } else {
            int l, r, tans = 0;
            cin>>l>>r;
            l--; r--;
            REP(kk,26) {
                char tmpc = 'a' + kk;
                // auto itr = lower_bound(mp[tmpc].begin(), mp[tmpc].end(), l);     // before
                auto itr = mp[tmpc].lower_bound(l);                                 // after
                /*if (itr != mp[tmpc].end()) {
                    debug(tmpc);
                    debug(*itr);
                }*/
                if (itr != mp[tmpc].end() && *itr <= r)
                    tans++;
            }
            cout<<tans<<endl;
        }
    }


    return 0;
}