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 rep(i,n) for (int i=0;i<(n);++i)
#define fi first
#define se second
#define INF 1000000009
#define lINF 1000000000000000009
typedef long long ll;
int n=1;
int dat[2000009];

void update(int i,int x){
  i+=n-1;
  dat[i]=(1<<x);
  while(i>0){
    i=(i-1)/2;
    dat[i]=dat[i*2+1]|dat[i*2+2];
  }
}

int query(int a,int b,int i,int l,int r){
  if(r<=a||b<=l)return 0;
  if(a<=l&&r<=b)return dat[i];
  else{
    int vl=query(a,b,i*2+1,l,(l+r)/2);
    int vr=query(a,b,i*2+2,(l+r)/2,r);
    return vl|vr;
  }
}

int main(){
  int m,q;
  string s;
  cin>>m>>s;
  while(n<m)n*=2;
  rep(i,n*2-1)dat[i]=0;
  rep(i,m){
    update(i,s[i]-'a');
  }
  cin>>q;
  rep(i,q){
    int com;
    cin>>com;
    if(com==1){
      int x;
      char c;
      cin>>x>>c;
      x--;
      update(x,c-'a');
    }
    else{
      int l,r;
      cin>>l>>r;
      l--;r--;
      int bits=query(l,r+1,0,0,n);
      cout<<__builtin_popcount(bits)<<endl;
    }
  }
  return(0);
}