#include <bits/stdc++.h>
#define REP(i, n)     for(int i = 0;i < n;i++)
#define REPR(i, n)    for(int i = n;i >= 0;i--)
#define FOR(i, m, n)  for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define VRSORT(v) sort(v.begin(), v.end(),greater<int>());
#define ALL(X) (X).begin(),(X).end()
#define INF 99999999
#define M_PI 3.14159265358979323846
#define MOD 1000000007

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 0};
int dy[]={0, 1, 0, -1, 0};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) os << el << " "; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T,S>& v) { for (auto el : v) os << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int N;
string S;
int QNUM;
struct query{
  int q,l,r,i;
  char c;
  query(int q):q(q){l=r=i=0;c='X';};
};

vector<query> Q;
map<char,vector<int>> C;
map<char,vector<int>> EC;
map<char,set<int>> Count;


void input(){
  #ifdef __LOCAL
      fs::path p = __FILE__;
      fs::path input,output;
      input = output = p.parent_path();
      input += string("/input/") + string(p.stem()) + string(".txt");
      output += string("/output/") + string(p.stem()) + string(".txt");
      freopen(input.c_str(), "r", stdin);
      freopen(output.c_str(), "w", stdout);
  #endif

  fast_io();
  cin >> N >> S >> QNUM;
  Q.assign(QNUM,0);
  REP(j,QNUM){
    cin >> Q[j].q;
    if(Q[j].q==1) {cin >> Q[j].i >> Q[j].c; Q[j].i--;}
    if(Q[j].q==2) {cin >> Q[j].l >> Q[j].r; Q[j].l--; Q[j].r--;}
  }
}


// int solve(){
//   REP(j,N) C[S[j]].push_back(j);
//   REP(j,QNUM) {
//     if(Q[j].q==1){
//       if(Q[j].c==S[Q[j].i]) continue;
//       EC[S[Q[j].i]].push_back(Q[j].i);
//       S[Q[j].i] = Q[j].c;
//       C[Q[j].c].push_back(Q[j].i);
//     }
//     if(Q[j].q==2){
//       int num=0;
//       for(char x='a';x<='z';x++){
//         VSORT(C[x])
//         VSORT(EC[x])
//         int numX,e_numX;
//         numX = upper_bound(ALL(C[x]),Q[j].r) - lower_bound(ALL(C[x]),Q[j].l);
//         e_numX = upper_bound(ALL(EC[x]),Q[j].r) - lower_bound(ALL(EC[x]),Q[j].l);
//         num += (numX-e_numX)>=1?1:0;
//       }
//       cout << (num) << endl;
//     }
//   }  
//   return 0;
// }


int solve(){
  REP(j,N) Count[S[j]].insert(j);
  REP(j,QNUM) {
    if(Q[j].q==1){
      if(S[Q[j].i]==Q[j].c) continue;
      Count[S[Q[j].i]].erase(Q[j].i);
      S[Q[j].i] = Q[j].c;
      Count[Q[j].c].insert(Q[j].i);
    }
    if(Q[j].q==2){
      int num=0;
      for(char x='a';x<='z';x++){
        if(Count[x].size()==0) continue;
        auto Left = Count[x].lower_bound(Q[j].l);
        // auto Right = Count[x].upper_bound(Q[j].r);
        // DBG(x)
        // DBG(S)
        // DBG(Q[j].l)
        // DBG(*Left)
        // DBG(Q[j].r)
        if(Left==Count[x].end()) continue;
        num += (*Left)<=(Q[j].r)?1:0;
      }
      cout << (num) << endl;
    }
  }  
  return 0;
}

int main()
{
  input();
  solve();
  return 0;
}


Measured memory_bytes: 24604