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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>

template <typename T, typename = void>
struct is_iterable : std::false_type {};
template <typename T>
struct is_iterable<T, std::void_t<decltype(std::begin(std::declval<T>())),
                                  decltype(std::end(std::declval<T>()))>>
    : std::true_type {};

template <typename T, typename = void>
struct is_pair : std::false_type {};
template <typename T>
struct is_pair<T, std::void_t<decltype(std::declval<T>().first),
                              decltype(std::declval<T>().second)>>
    : std::true_type {};

template <typename T>
void debug(T&& v) {
  if constexpr (is_pair<T>::value) {
    std::cerr << "{";
    debug(v.first);
    std::cerr << ", ";
    debug(v.second);
    std::cerr << "}";
  } else if constexpr (is_iterable<T>::value &&
                       !std::is_same<T, std::string>::value) {
    std::cerr << "{";
    for (auto it = std::begin(v); it != std::end(v); ++it) {
      if (it != std::begin(v)) std::cerr << ", ";
      debug(*it);
    }
    std::cerr << "}";
  } else {
    std::cerr << v;
  }
}
template <typename T, typename... Ts>
void debug(T&& value, Ts&&... args) {
  debug(value);
  std::cerr << ", ";
  debug(args...);
}
#if DEBUG
#define dbg(...)                        \
  do {                                  \
    cerr << #__VA_ARGS__ << ": ";       \
    debug(__VA_ARGS__);                 \
    cerr << " (L" << __LINE__ << ")\n"; \
  } while (0)
#else
#define dbg(...)
#endif

void read_from_cin() {}
template <typename T, typename... Ts>
void read_from_cin(T& value, Ts&... args) {
  std::cin >> value;
  read_from_cin(args...);
}
#define rd(type, ...) \
  type __VA_ARGS__;   \
  read_from_cin(__VA_ARGS__);
#define ints(...) rd(int, __VA_ARGS__);
#define strings(...) rd(string, __VA_ARGS__);

template <typename T>
void write_to_cout(const T& value) {
  if constexpr (std::is_same<T, bool>::value) {
    std::cout << (value ? "Yes" : "No");
  } else {
    std::cout << value;
  }
}
template <typename T, typename... Ts>
void write_to_cout(const T& value, const Ts&... args) {
  write_to_cout(value);
  std::cout << ' ';
  write_to_cout(args...);
}
#define wt(...)                 \
  do {                          \
    write_to_cout(__VA_ARGS__); \
    cout << '\n';               \
  } while (0)

#define all(x) (x).begin(), (x).end()

#define rep_dispatch(_1, _2, _3, name, ...) name
#define rep3(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep2(i, n) rep3(i, 0, n)
#define rep1(n) rep2(_loop_variable_, n)
#define rep(...) rep_dispatch(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; --i)

template <typename T>
std::istream& operator>>(std::istream& is, std::vector<T>& v) {
  for (T& vi : v) is >> vi;
  return is;
}

template <typename T, typename U>
std::istream& operator>>(std::istream& is, std::pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T, typename U>
bool chmax(T& a, U b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T, typename U>
bool chmin(T& a, U b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T>
int sz(const T& v) {
  return v.size();
}

template <typename T>
int popcount(T i) {
  return std::bitset<std::numeric_limits<T>::digits>(i).count();
}

#include <boost/hana/functional/fix.hpp>
const auto& Fix = boost::hana::fix;

using ll = long long;

template <typename T>
using low_priority_queue =
    std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <typename T>
using V = std::vector<T>;
template <typename T>
using VV = V<V<T>>;

template <typename T>
class SegmentTree {
 public:
  using Operation = std::function<T(T, T)>;
  SegmentTree(int size, Operation operation, T identity = T())
      : operation_(operation), identity_(identity) {
    int two = 1;
    while (two < size) {
      two <<= 1;
    }
    v_.resize(two * 2 - 1, identity_);
  }
  void Set(int i, T v) {
    int index = v_.size() / 2 + i;
    while (true) {
      v_[index] = v;
      if (index == 0) break;
      v = operation_(v, v_[index + (index % 2 == 0 ? -1 : 1)]);
      index = (index - 1) / 2;
    }
  }
  T Get(int i) const { return Aggregate(i, i + 1); }
  T Aggregate(int begin, int end) const {
    std::function<T(int, int, int)> rec = [&](int cbegin, int cend, int index) {
      if (begin <= cbegin && cend <= end) {
        return v_[index];
      }
      if (cend <= begin || end <= cbegin) {
        return identity_;
      }
      int cmid = (cbegin + cend) / 2;
      return operation_(rec(cbegin, cmid, index * 2 + 1),
                        rec(cmid, cend, index * 2 + 2));
    };
    return rec(0, (v_.size() + 1) / 2, 0);
  }

 private:
  const Operation operation_;
  const T identity_;
  std::vector<T> v_;
};

using namespace std;

int Union(int a, int b) { return a | b; }

int main() {
  ints(N);
  SegmentTree<int> tree(N, Union);
  strings(S);
  rep(i, N) tree.Set(i, 1 << (S[i] - 'a'));
  ints(Q);
  rep(Q) {
    ints(t);
    if (t == 1) {
      ints(i);
      char c;
      cin >> c;
      tree.Set(i - 1, 1 << (c - 'a'));
    } else {
      ints(l, r);
      wt(popcount(tree.Aggregate(l - 1, r)));
    }
  }
}