#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
const int inf = 1e9 + 7;
const ll INF = 1e18;
#define abs(x) (x >= 0 ? x : -(x))
#define lb(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define ub(v, x) (int)(upper_bound(all(v), x) - v.begin())
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { if (a < b) { a = b; return 1; } return 0; }
template<typename T> T gcd(T a, T b) { if (b == 0) return a; return gcd(b, a % b); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
template<typename T> T pow(T a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
const int mod = 1000000007;
ll modpow(ll a, int b) { return b ? modpow(a * a % mod, b / 2) * (b % 2 ? a : 1) % mod : 1; }
template<class T> ostream& operator<<(ostream& os, const vector<T>& vec) { rep(i, sz(vec)) { if (i) os << " "; os << vec[i]; } return os; }
template<class T, class U> ostream& operator<<(ostream& os, const pair<T, U>& p) { os << p.F << " " << p.S; return os; }
template<class T> inline void add(T &a, int b) { a += b; if (a >= mod) a -= mod; }



void solve();

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cout << fixed << setprecision(10);

  int T;
  // cin >> T;
  T = 1;

  while (T--) {
      solve();
  }
}

template<typename T>
class SegTree {
    int n;
    T def;
    function<T(T, T)> operation;
    vector<T> data;

    T _query(int a, int b, int k, int l, int r) {
        if (r <= a || b <= l) return def;
        if (a <= l && r <= b) return data[k];
        T c1 = _query(a, b, 2 * k + 1, l, (l + r) / 2);
        T c2 = _query(a, b, 2 * k + 2, (l + r) / 2, r);
        return operation(c1, c2);
    }

public:
    SegTree<T>(int _n, T _def, function<T(T, T)> _operation)
    : def(_def), operation(_operation) {
        n = 1;
        while (n < _n) n *= 2;
        data = vector<T>(2 * n - 1, def);
    }

    T query(int a, int b) {
        return _query(a, b, 0, 0, n);
    }

    void change(int i, T x) {
        i += n - 1;
        data[i] = x;
        while (i > 0) {
            i = (i - 1) / 2;
            data[i] = operation(data[i * 2 + 1], data[i * 2 + 2]);
        }
    }

    T operator[](int i) { return data[i + n - 1]; }
    void out() { rep(i, n) cout << bitset<26>(data[i + n - 1]) << " "; cout << endl; }
};

void solve() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  SegTree<int> sgt(n, 0, [](int a, int b) { return a | b; });
  rep(i, n) sgt.change(i, 1 << (s[i] - 'a'));
  // sgt.out();
  int q;
  cin >> q;
  while (q--) {
    int key;
    cin >> key;
    if (key == 1) {
      int i;
      char c;
      cin >> i >> c;
      i--;

      sgt.change(i, 0);
      sgt.change(i, 1 << (c - 'a'));
      // sgt.out();
      s[i] = c;
      continue;
    }

    int l, r;
    cin >> l >> r;
    l--; r--;
    cout << __builtin_popcount(sgt.query(l, r + 1)) << endl;
  }
}


Measured memory_bytes: 5020