#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <numeric>
#include <tuple>

template <class T, class U>
inline bool chmin(T& lhs, const U& rhs) {
  if (lhs > rhs) {
    lhs = rhs;
    return true;
  }
  return false;
}

template <class T, class U>
inline bool chmax(T& lhs, const U& rhs) {
  if (lhs < rhs) {
    lhs = rhs;
    return true;
  }
  return false;
}

// [l, r) from l to r
struct range {
  struct itr {
    int i;
    constexpr itr(int i_): i(i_) { }
    constexpr void operator ++ () { ++i; }
    constexpr int operator * () const { return i; }
    constexpr bool operator != (itr x) const { return i != x.i; }
  };
  const itr l, r;
  constexpr range(int l_, int r_): l(l_), r(std::max(l_, r_)) { }
  constexpr itr begin() const { return l; }
  constexpr itr end() const { return r; }
};

// [l, r) from r to l
struct revrange {
  struct itr {
    int i;
    constexpr itr(int i_): i(i_) { }
    constexpr void operator ++ () { --i; }
    constexpr int operator * () const { return i; }
    constexpr bool operator != (itr x) const { return i != x.i; }
  };
  const itr r, l;
  constexpr revrange(int l_, int r_): l(l_ - 1), r(std::max(l_, r_) - 1) { }
  constexpr itr begin() const { return r; }
  constexpr itr end() const { return l; }
};

template <class T>
class segment_tree {
public:
  using value_type = typename T::value_type;
  using effector_type = typename T::effector_type;
  using value_operation = typename T::value_operation;
  using merge_operation = typename T::merge_operation;

private:
  int size;
  const value_operation op1;
  const merge_operation op2;
  std::vector<value_type> node;

  void update() {
    for (int k = size - 1; k > 0; --k) {
      node[k] = op1(node[k << 1 | 0], node[k << 1 | 1]);
    }
  }

public:
  segment_tree(): op1(value_operation()), op2(merge_operation()) { }
  segment_tree(int size_, const value_type &initial_ = value_operation().identity):
    op1(value_operation()), op2(merge_operation())
  { init(size_, initial_); }
  segment_tree(const std::vector<value_type> &node_):
    op1(value_operation()), op2(merge_operation())
  { build(node_); }

  void init(int size_, const value_type &initial_ = value_operation().identity) {
    size = 1;
    while (size < size_) {
      size <<= 1;
    }
    node.assign(size << 1, initial_);
    if (initial_ != value_operation().identity) {
      update();
    }
  }
  void build(const std::vector<value_type> &node_) {
    init(node_.size());
    assign(node_.begin(), node_.end(), 0);
  }

  void modify(int i, const effector_type &x) {
    i += size;
    node[i] = op2(node[i], x);
    while (i > 1) {
      i >>= 1;
      node[i] = op1(node[i << 1 | 0], node[i << 1 | 1]);
    }
  }
  template <class U>
  void modify(U begin, U end, int i) {
    i += size;
    while (begin != end) {
      node[i] = op2(node[i], *begin);
      ++i;
      ++begin;
    }
    update();
  }

  void assign(int i, const value_type &x) {
    i += size;
    node[i] = x;
    while (i > 1) {
      i >>= 1;
      node[i] = op1(node[i << 1 | 0], node[i << 1 | 1]);
    } 
  }
  template <class U>
  void assign(U begin, U end, int i) {
    i += size;
    while (begin != end) {
      node[i] = *begin;
      ++i;
      ++begin;
    }
    update();
  }

  value_type operator [] (int i) const { 
    return node[i + size];
  }
  value_type fold(int l, int r) const {
    l += size;
    r += size;
    value_type resl = op1.identity;
    value_type resr = op1.identity;
    while (l < r) {
      if (l & 1) {
        resl = op1(resl, node[l++]);
      }
      if (r & 1) {
        resr = op1(node[--r], resr);
      }
      l >>= 1;
      r >>= 1;
    }
    return op1(resl, resr);
  }

};

struct monoid {
  using value_type = int;
  using effector_type = char;
  struct value_operation {
    value_type identity = 0;
    value_type operator () (const value_type &x, const value_type &y) const {
      return x | y;
    }
  };
  struct merge_operation {
    value_type operator () (const value_type &x, const effector_type &y) const {
      int t = y - 'a';
      return 1 << t;
    }
  };
};

int main() {
  int N, Q;
  std::string S;
  std::cin >> N >> S >> Q;
  segment_tree<monoid> seg(N);
  for (int i: range(0, N)) {
    seg.modify(i, S[i]);
  }
  while (Q--) {
    int t;
    std::cin >> t;
    if (t == 1) {
      int i;
      char c;
      std::cin >> i >> c;
      seg.modify(i - 1, c);
    }
    else {
      int l, r;
      std::cin >> l >> r;
      std::cout << __builtin_popcount(seg.fold(l - 1, r)) << '\n';
    }
  }
  return 0;
}


Measured memory_bytes: 4996