#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<LL, LL> PII;

// chmax, chmin
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return 1;
  }
  return 0;
}

template <typename T>
function<T(T, T)> op_max = [](T a, T b) -> T { return max(a, b); };
template <typename T>
function<T(T, T)> op_min = [](T a, T b) -> T { return min(a, b); };

template <typename T>
function<T(T, T)> op_sum = [](T a, T b) -> T { return a + b; };

namespace detail
{
  template <typename T, std::size_t NDIMS>
  struct vector_builder
  {
    using type = std::vector<typename vector_builder<T, NDIMS - 1>::type>;

    static type make(std::vector<std::size_t> dims, const T &v = {})
    {
      const auto vec = std::vector<T>(dims.empty() ? 0 : dims.back(), v);
      if (!dims.empty())
        dims.pop_back();
      return vector_builder<std::vector<T>, NDIMS - 1>::make(dims, vec);
    }
  };

  template <typename T>
  struct vector_builder<T, 1>
  {
    using type = std::vector<T>;

    static type make(std::vector<std::size_t> dims, const T &v = {})
    {
      return type(dims.empty() ? 0 : dims.back(), v);
    }
  };
} // namespace detail

template <typename T, typename... SIZE_T>
auto exvector(const T &v, SIZE_T... dims)
{
  static_assert(sizeof...(dims) != 0, "invalid dimension");
  std::vector<std::size_t> vec_dims{dims...};
  return detail::vector_builder<T, sizeof...(dims)>::make(vec_dims, v);
}

using namespace std;
//********************  dumps ************************//

template <typename T>
void dump(const T &data, vector<int> &iter)
{
  cout << data << " ";
}
template <typename T>
void dump(const vector<T> &data, vector<int> &iter)
{
  for (auto elem : data)
    dump(elem, iter);
  cout << endl;
}

template <typename T>
void dump(const vector<vector<T>> &data, vector<int> &iter)
{
  for (auto elem : iter)
  {
    cout << "[" << elem << "]";
  }
  cout << endl;
  for (int i = 0; i < data.size(); i++)
  {
    iter.push_back(i);
    dump(data[i], iter);
    iter.pop_back();
  }
  cout << endl;
}

template <typename T>
void dump(const vector<T> &data, int dummy)
{
  for (int i = 0; i < data.size(); i++)
  {
    cout << "[" << i << "] " << data[i] << endl;
  }
}
template <typename T>
void dump(const T &data)
{ // T : data, U = base type val.
  vector<int> iter;
  dump(data, iter);
}
///////////////////////////////////////////////

template <typename T>
class SegmentTree
{
  int N;
  vector<T> dat;
  function<T(T, T)> oper;
  T identity;

public:
  SegmentTree(int n, function<T(T, T)> op, T id)
  {
    oper = op;
    identity = id;
    N = 1;
    while (N < n)
      N *= 2;
    dat.resize(2 * N, identity);
  }
  // update k th element, 0-indexed
  void update(int k, T a)
  {
    k += N - 1; // leaf
    dat[k] = a;
    while (k > 0)
    {
      k = (k - 1) / 2;
      dat[k] = oper(dat[k * 2 + 1], dat[k * 2 + 2]);
    }
  }
  // query[a, b), 0-indexed
  T query(int a, int b) { return query(a, b, 0, 0, N); }
  T query(int a, int b, int k, int l, int r)
  {
    if (r <= a || b <= l)
      return identity;
    if (a <= l && r <= b)
      return dat[k];
    int m = (l + r) / 2;
    return oper(query(a, b, k * 2 + 1, l, m), query(a, b, k * 2 + 2, m, r));
  }
};

int main()
{

  cout << setprecision(10);
  // Failed to predict input format

  int N;
  cin >> N;
  string s;
  cin >> s;

  auto oper = [](int a, int b) { return a + b; };

  vector<SegmentTree<int>>
      seg(26, SegmentTree<int>(N, oper, 0));

  for (int i = 0; i < s.size(); i++)
  {
    int val = s[i] - 'a';
    seg[val].update(i, 1);
  }

  int Q;
  cin >> Q;
  for (int z = 0; z < Q; z++)
  {

    int info;
    cin >> info;
    if (info == 1)
    {
      int b;
      string t;
      cin >> b >> t;
      b--;
      int prev = s[b] - 'a';
      int next = t[0] - 'a';
      seg[prev].update(b, 0);
      seg[next].update(b, 1);
      s[b] = t[0];
      continue;
    }
    int b, c;
    cin >> b >> c;
    b--;
    c--;

    int ans = 0;
    for (int i = 0; i < 26; i++)
    {
      int val = seg[i].query(b, c + 1);
      if (val)
        ans++;
    }
    cout << ans << endl;
  }

  return 0;
}


Measured memory_bytes: 111620