/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author aajisaka
 */

#include<bits/stdc++.h>

using namespace std;

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#define SPEED ios_base::sync_with_stdio(false);cin.tie(nullptr)
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

using ll = long long;
using P = pair<ll, ll>;

constexpr long double PI = 3.14159265358979323846264338327950288L;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
// Segment Tree for query sum[a, b)
template<typename T>
class SegTree {
    using F = function<T(T, T)>;
    int N;
    vector<T> dat;
    const F f;  // merge monoids
    const T ID; // identity

    // RangeSumQuery:
    // auto f = [](ll a, ll b) { return a+b; };
    // auto ID = 0LL;

    // RangeMaximumQuery:
    // auto f = [](ll a, ll b) { return max(a, b); };
    // auto ID = 0LL; (sometimes it should be LLONG_MIN)

    // RangeMinimumQuery:
    // auto f = [](ll a, ll b) { return min(a, b); };
    // auto ID = LLONG_MAX;

    // auto seg = SegTree<ll>(100000, f, ID);
public: SegTree(int n, const F f, const T& ID) : f(f), ID(ID) {
    N = 1;
    while(N < n) N *= 2;
    dat.resize(2*N-1, ID);
  }

public: void build(vector<T>& a) {
    int n = a.size();
    for(int i=0; i<n; i++) dat[i+N-1] = a[i];
    for(int i=N-2; i>=0; i--) dat[i] = f(dat[i*2+1], dat[i*2+2]);
  }

  // update k-th element
public: void update(int k, const T& a) {
    k += N-1;
    dat[k] = a;
    while(k > 0) {
      k = (k-1)/2;
      dat[k] = f(dat[k*2+1], dat[k*2+2]);
    }
  }

  // add k-th element by a
public: void add(int k, const T& a) {
    k += N-1;
    dat[k] = f(dat[k], a);
    while(k > 0) {
      k = (k-1)/2;
      dat[k] = f(dat[k*2+1], dat[k*2+2]);
    }
  }

  // return sum[a, b)
public: T query(int a, int b) {
    return query(a, b, 0, 0, N);
  }
public: T query(int a, int b, int k, int l, int r) {
    if (r <= a || b <= l) return ID;
    if (a <= l && r <= b) return dat[k];
    auto m = (l+r)/2;
    return f(query(a, b, k*2+1, l, m), query(a, b, k*2+2, m, r));
  }
};

class ESimpleStringQueries {
public:
    void solve(istream& cin, ostream& cout) {
      SPEED;
      int n; cin >> n;
      string s; cin >> s;
      // RangeSumQuery:
      auto f = [](ll a, ll b) { return a+b; };
      auto ID = 0LL;

      // RangeMaximumQuery:
      // auto f = [](ll a, ll b) { return max(a, b); };
      // auto ID = 0LL; (sometimes it should be LLONG_MIN)

      // RangeMinimumQuery:
      // auto f = [](ll a, ll b) { return min(a, b); };
      // auto ID = LLONG_MAX;

      vector<SegTree<ll>> vec(26, SegTree<ll>(n, f, ID));

      rep(i, n) {
        int k = (s[i]-'a');
        vec[k].update(i, 1);
      }
      int q; cin >> q;
      rep(i, q) {
        int kind; cin >> kind;
        if (kind == 1) {
          int pos; cin >> pos;
          pos--;
          char c; cin >> c;
          vec[(s[pos]-'a')].update(pos, 0);
          vec[c-'a'].update(pos, 1);
          s[pos] = c;
        } else {
          int l, r; cin >> l >> r;
          int ret = 0;
          rep(j, 26) {
            if (vec[j].query(l-1, r) > 0) ret++;
          }
          cout << ret << '\n';
        }


      }
    }
};

signed main() {
  ESimpleStringQueries solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}

Measured memory_bytes: 222108