#pragma target("avx")
#include <bits/stdc++.h>

using namespace std;

typedef int ll;
typedef long double ld;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef unordered_map<ll, ll> U_MAP;
typedef priority_queue<ll> pq;
typedef priority_queue<ll, vector<ll>, greater<ll>> rpq;
const int INF = 1e9, MOD = 1e9 + 7, ohara = 1e6 + 10;
const ll LINF = 1e18;

#define rep(i, n) for (ll(i) = 0; (i) < (int)(n); (i)++)
#define rrep(i, a, b) for (ll i = (a); i < (b); i++)
#define rrrep(i, a, b) for (ll i = (a); i >= (b); i--)
#define all(v) (v).begin(), (v).end()
#define Size(n) (n).size()
#define Cout(x) cout << (x) << endl
#define doublecout(a) cout << fixed << setprecision(15) << a << endl;
#define fi first
#define se second
#define m_p make_pair
#define p_b push_back
string to_string(string s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

//------ Believe yourself as a genius!!!!!! ------

struct SegmentTree {
  int siz;
  vector<ll> node;
  SegmentTree(int n, ll init) {
    siz = 1;
    while (siz < n) siz <<= 1;
    node.assign(2 * siz, init);
  }

  void update(int k, ll x) {
    k += siz - 1;
    node[k] = x;
    while (k > 0) {
      k = (k - 1) / 2;
      node[k] = min(node[2 * k + 1], node[2 * k + 2]);
    }
  }

  ll query(int a, int b, int k = 0, int l = 0, int r = -1) {
    if (r < 0) r = siz;
    if (r <= a || b <= l) return LINF;
    if (a <= l && r <= b) return node[k];
    ll vl = query(a, b, 2 * k + 1, l, (l + r) / 2);
    ll vr = query(a, b, 2 * k + 2, (l + r) / 2, r);
    return min(vl, vr);
  }
};

int dy[] = {1, 0, -1, 0};
int dx[] = {0, 1, 0, -1};
// int dy[]={-1,0,1,-1,1,-1,0,1};int dx[]={-1,-1,-1,0,0,1,1,1};
string alph("abcdefghijklmnopqrstuvwxyz"), s;
ll n, cnt, ans, a, b, c, d, tmp, m, h, w, x, y, sum, k, q, l, r, tmp2;
ll bucket[30][30000];
const int B = 800;
char z;

int main(void) {
  cin.tie(0);
  cout.tie(0);
  ios::sync_with_stdio(false);

  cin >> n >> s >> q;
  rep(i, n) {
    rep(j, Size(alph)) {
      if (alph[j] == s[i]) tmp = j;
    }
    bucket[tmp][i / B]++;
  }
  rep(i, q) {
    cin >> a;
    if (a == 1) {
      cin >> b >> z;
      b--;
      rep(j, Size(alph)) {
        if (alph[j] == z) {
          tmp = j;
        }
        if (alph[j] == s[b]) {
          tmp2 = j;
        }
      }
      bucket[tmp][b / B]++;
      s[b] = z;
      bucket[tmp2][b / B]--;
    } else {
      bool vi[100] = {};
      cin >> b >> c;
      // index-[b,c]内の総和ansを求める
      b--;
      c--;
      //端を揃えます
      while (1) {
        if (b > c) break;
        if (b % B == 0) break;
        vi[s[b] - '0'] = true;
        b++;
      }
      while (1) {
        if (b > c) break;
        vi[s[c] - '0'] = true;
        if (c % B == 0) break;
        c--;
      }
      ll hozib = b, hozic = c;
      cnt = 0;
      rep(i, Size(alph)) {
        ans = 0;
        b = hozib;
        c = hozic;
        if (vi[alph[i] - '0']) {
          cnt++;
          continue;
        }

        //バケットをみる
        while (1) {
          if (b == c || b > c) break;
          int bb = b / B;
          ans += bucket[i][bb];
          if (ans >= 1) break;
          b += B;
        }
        if (ans >= 1) cnt++;
      }
      Cout(cnt);
    }
  }
  return 0;
}


Measured memory_bytes: 1172