#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define call(var) cerr<<#var<<"="<<var<<endl;
#define dup(x,y) (((x)+(y)-1)/(y))
using ll=long long;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using Graph = vector<vi>;
using P = pair<int,int>;
const int MOD=(int)1e9+7;
const int INF=(int)1e9;
const ll LINF=(ll)1e18;
template<class t,class u> inline bool chmax(t&a,u b){if(a<b){a=b;return true;}return false;}
template<class t,class u> inline bool chmin(t&a,u b){if(b<a){a=b;return true;}return false;}

template< typename Monoid >
struct SegmentTree {
  using F = function< Monoid(Monoid, Monoid) >;

  int sz;
  vector< Monoid > seg;

  const F f;
  const Monoid M1;

  SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1) {
    sz = 1;
    while(sz < n) sz <<= 1;
    seg.assign(2 * sz, M1);
  }

  void set(int k, const Monoid &x) {
    seg[k + sz] = x;
  }

  void build() {
    for(int k = sz - 1; k > 0; k--) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  void update(int k, const Monoid &x) {
    k += sz;
    seg[k] = x;
    while(k >>= 1) {
      seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
    }
  }

  Monoid query(int a, int b) {
    Monoid L = M1, R = M1;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) L = f(L, seg[a++]);
      if(b & 1) R = f(seg[--b], R);
    }
    return f(L, R);
  }

  Monoid operator[](const int &k) const {
    return seg[k + sz];
  }

  template< typename C >
  int find_subtree(int a, const C &check, Monoid &M, bool type) {
    while(a < sz) {
      Monoid nxt = type ? f(seg[2 * a + type], M) : f(M, seg[2 * a + type]);
      if(check(nxt)) a = 2 * a + type;
      else M = nxt, a = 2 * a + 1 - type;
    }
    return a - sz;
  }


  template< typename C >
  int find_first(int a, const C &check) {
    Monoid L = M1;
    if(a <= 0) {
      if(check(f(L, seg[1]))) return find_subtree(1, check, L, false);
      return -1;
    }
    int b = sz;
    for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
      if(a & 1) {
        Monoid nxt = f(L, seg[a]);
        if(check(nxt)) return find_subtree(a, check, L, false);
        L = nxt;
        ++a;
      }
    }
    return -1;
  }

  template< typename C >
  int find_last(int b, const C &check) {
    Monoid R = M1;
    if(b >= sz) {
      if(check(f(seg[1], R))) return find_subtree(1, check, R, true);
      return -1;
    }
    int a = sz;
    for(b += sz; a < b; a >>= 1, b >>= 1) {
      if(b & 1) {
        Monoid nxt = f(seg[--b], R);
        if(check(nxt)) return find_subtree(b, check, R, true);
        R = nxt;
      }
    }
    return -1;
  }
};

int main(){
    int n,Q;
    string s;cin >> n >> s >> Q;
    vector<SegmentTree<bool>> seg(26, SegmentTree<bool>(n, [](bool a, bool b){return a|b;}, false));
    rep(i,n){
        seg[s[i]-'a'].set(i, true);
    }
    rep(i,26) seg[i].build();

    while(Q--){
        int q;cin >> q;
        if(q == 1){
            int i;
            char c;cin >> i >> c;
            --i;
            rep(j,26){
                if(seg[j][i] == 1){
                    seg[j].update(i, 0);
                    break;
                }
            }
            seg[c-'a'].update(i, true);
        }else{
            int l,r;cin >> l >> r;
            --l;--r;
            int ans = 0;
            rep(i,26){
                if(seg[i].query(l, r+1)) ++ans;
            }
            //cerr << "ans is ";
            cout << ans << "\n";
        }
    }
}

Measured memory_bytes: 4356