#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <functional>
#include <bitset>

using namespace std;
using lint = long long int;
long long int INF = 1001001001001001LL;
int inf = 1000000007;
long long int MOD = 1000000007LL;
double PI = 3.1415926535897932;

template<typename T1,typename T2>inline void chmin(T1 &a,const T2 &b){if(a>b) a=b;}
template<typename T1,typename T2>inline void chmax(T1 &a,const T2 &b){if(a<b) a=b;}

#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()

/* do your best */

// quoted from beet-aizu
template <typename T, typename E, typename F, typename G>
struct SegmentTree{
    // using F = function<T(T, T)>
    // using G = function<T(T, E)>
    int n;
    F f;
    G g;
    T ti;
    vector<T> dat;
    SegmentTree(){};
    SegmentTree(F f,G g,T ti):f(f),g(g),ti(ti){}
    void init(int n_){    
        n=1;
        while(n<n_) n<<=1;
        dat.assign(n<<1,ti);
    }
    void build(const vector<T> &v){
        int n_=v.size();
        init(n_);
        for(int i=0;i<n_;i++) dat[n+i]=v[i];
        for(int i=n-1;i;i--)
            dat[i]=f(dat[(i<<1)|0],dat[(i<<1)|1]);
    }
    void update(int k,const E &x){
        k += n;
        dat[k] = g(dat[k], x);
        while(k>>=1)
            dat[k]=f(dat[(k<<1)|0],dat[(k<<1)|1]);    
    }
    T operator [](int k) const { return dat[k+n]; }
    T query(int a,int b) const {
        T vl=ti,vr=ti;
        for(int l=a+n,r=b+n;l<r;l>>=1,r>>=1) {
            if(l&1) vl=f(vl,dat[l++]);
            if(r&1) vr=f(dat[--r],vr);
        }
        return f(vl,vr);
    }

    /* TODO わからない 聞く 
    template<typename C>
    int find(int a,int b,C &check,int k,int l,int r){
        if(!check(dat[k])||r<=a||b<=l) return -1;
        if(k>=n) return k-n;
        int m=(l+r)>>1;
        int vl=find(a,b,check,(k<<1)|0,l,m);
        if(~vl) return vl;
        return find(a,b,check,(k<<1)|1,m,r);
    }
    template<typename C>
    int find(int a,int b,C &check){
        return find(a,b,check,1,0,n);
    }*/
    
};

int main(){
  using T = lint;  // type T
  using E = lint;  // type E
  auto f = [](T a, T b){ // return type T value
    return a + b;
  };
  auto g = [](T a, E b){ // return type T value
    return b;  // return b;
  };
  T ti = 0;  // identify element
  
  vector<SegmentTree<T, E, decltype(f), decltype(g)>> sg(26, SegmentTree<T, E, decltype(f), decltype(g)>(f, g, ti));  // don't change
    
  int n; cin >> n;
  string s; cin >> s;

  for(int i = 0; i < 26; i++) {
    
    vector<lint> dat(n, 0);
    for(int j = 0; j < n; j++) {
      lint num = s[j] - 'a';
      if(num == i) dat[j]++;
    }
    sg[i].build(dat);
  }

  int q; cin >> q;
  for(int l = 0; l < q; l++) {

    int op; cin >> op;
    if(op == 1) {
      // update
      int i;
      char c; cin >> i >> c;
      i--;
      lint num = c - 'a';
      for(int j = 0; j < 26; j++) sg[j].update(i, 0);
      sg[num].update(i, 1);
    } else {
      int l, r; cin >> l >> r;
      lint ans = 0;
      l--;
      for(int j = 0; j < 26; j++) {
        if(sg[j].query(l, r) > 0) ans++;
      }
      cout << ans << endl;
    }
  }
}


Measured memory_bytes: 217792