#include "bits/stdc++.h"
#include <unordered_set>
#define rep(i,n) for(int i = 0; i < n; i++)
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define vll vector<vector<long long>>
#define vl vector<long long>
#define vi vector<int>
#define vii vector<vector<int>>
#define pb push_back
#define pf push_front
#define ld long double
#define Sort(a) sort(a.begin(),a.end())
#define cSort(a,cmp) sort(a.begin(),a.end(),cmp)
#define reSort(a) sort(a.rbegin(), a.rend())
static const ll llMAX = numeric_limits<long long>::max();
static const int intMAX = numeric_limits<int>::max();
static const ll  llMIN = numeric_limits<long long>::min();
static const int intMIN = numeric_limits<int>::min();
static const ll d_5 = 100000;
static const ll d9_7 = 1000000007;
static const ll d_9 = 1000000000;
static const double PI=3.14159265358979323846;

template<class T>
void Printvector(std::vector<T> a){
  int size = a.size();
  rep(i,size){
    cout<<a[i]<<" ";
  }
  cout<<endl;
}
template<class T>
void Printvector(std::vector<std::vector<T>> a){
  int size = a.size();
  rep(i,size){
    int size2=a[i].size();
    rep(j,size2){
      cout<<a[i][j]<<" ";
    }
    cout<<endl;
  }
  cout<<endl;
}
ll digitpower(ll a,ll b){//aのb乗を計算
  if(b==1){
    return a;
  }else if(b==0){
    return 1;
  }
  int mode=0;
  if(b%2==1){
    ll tmp = digitpower(a,(b-1)/2);
    if(mode==1){
      tmp%=d9_7;
    }
    tmp*=tmp;
    if(mode==1){
      tmp%=d9_7;
    }
    tmp*=a;
    if(mode==1){
      return tmp%d9_7;
    }else{
      return tmp;
    }
  }else{
    ll tmp = digitpower(a,(b)/2);
    if(mode==1){
      tmp%=d9_7;
    }
    tmp*=tmp;
    if(mode==1){
      tmp%=d9_7;
    }
    if(mode==1){
      return tmp%d9_7;
    }else{
      return tmp;
    }
  }
}

vl facs(2000010,-1);
ll Factrial(ll num){
  if(facs[num]!=-1){
    return facs[num];
  }
  if(num==1||num<=0){
    return 1;
  }else if(num<0){
    printf("ERROR_minus\n");
    return 0;
  }else{
    facs[num]=(num*Factrial(num-1))%d9_7;
    return facs[num];
  }
}
long long modinv(long long a, long long m) {//modの逆元

    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m; 
    if (u < 0) u += m;
    return u;
}

vl invs(2000010,-1);
ll linercomb(ll n,ll k, ll mod){//n,kの線形時間で求める
if(n<k)return 0;
if(n<0)return 0;
if(k==0 || k==n)return 1;
  ll ans=Factrial(n);
  if(invs[k]==-1){
    invs[k]=modinv(Factrial(k),mod);
  }
  ans*=invs[k];
  ans%=d9_7;
  ll k1=Factrial(n-k);
  k1%=mod;
  ans*=modinv(k1,mod);
  ans%=mod;
  return ans;
}
unordered_map<ll,ll> prime_factor(int64_t n) {
  unordered_map<ll,ll> ret;
  for(int64_t i = 2; i * i <= n; i++) {
    while(n % i == 0) {
      ret[i]++;
      n /= i;
    }
  }
  if(n != 1) ret[n] = 1;
  return ret;
}

template<class T>
vector<T> getaccum(vector<T> a){
  int size=a.size();
  vector<T> ans(size);
  ans[0]=a[0];
  for(int i=0;i<size-1;i++){
    ans[i+1]=ans[i]+a[i+1];
    //ans[i+1]%=d9_7;
  }
  return ans;
}

ll getaccumnum(vector<ll> accum,int l,int r){//閉区間[l,r]の総和
  if(l==0){
    return accum[r];
  }else{
    return accum[r]-accum[l-1];
  }
}

struct datas{
  ll p;
  ll q;
};/*
bool cmp(const datas &a, const datas &b)
{
    return a.num < b.num;
}*/
template<class T>
T gcd(T a,T b){
  if(a==0){
    return b;

  }else if(b==0){
    return a;
  }
  while(1) {
    if(a < b) swap(a, b);
    if(!b) break;
    a %= b;
  }
  return a;
}
int LCS(string s,string t) {
  int n=s.size();
  int m=t.size();
  vector<vector<int>> dp=vector<vector<int>>(n+1,vector<int>(m+1,0));
    for (int i=0; i<n; ++i) {
        for (int j=0; j<m; ++j) {
            if (s[i] == t[j]) {
                dp[i+1][j+1] = dp[i][j] + 1;
            }
            else {
                dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
            }
        }
    }
    return dp[n][m];
}

//Segment Tree
template<class T>
class SegmentTree{
  public:
   int n;
   vector<T> nodes;
    //constructor
    SegmentTree(int size,T init){
      initialize(size,init);
    }
    //関数を定義(minなのかmaxなのかとか)
    T thisoperator(T a, T b){
      return a+b;
    }
    void update(int x,T a){//xがindex
      x+=n-1;
      nodes[x]=a;
      while(x>0){
        x=(x-1)/2;
        nodes[x]=thisoperator(nodes[2*x+1],nodes[2*x+2]);
      }
    }
   void initialize(int inputn,T init){
      int k=0;
      while(inputn>(2<<k)){
        k++;
      }
      n=(2<<k);
      nodes=vector<T> ((2<<k)*2-1,init);
   }
   T sec_get(int reql,int reqr,int nowindex=0,int nowl=0,int nowr=-1){
     // 最初に呼び出されたときの対象区間は [0, n)
    if(nowr < 0) nowr = n;

    // 要求区間と対象区間が交わらない -> 適当に返す
    if(nowr <= reql || reqr <= nowl) return 0;

    // 要求区間が対象区間を完全に被覆 -> 対象区間を答えの計算に使う
    if(reql <= nowl && nowr <= reqr) return nodes[nowindex];
    // 要求区間が対象区間の一部を被覆 -> 子について探索を行う
    // 左側の子を vl ・ 右側の子を vr としている
    // 新しい対象区間は、現在の対象区間を半分に割ったもの
    T val1 = sec_get(reql, reqr, 2*nowindex+1, nowl, (nowl+nowr)/2);
    T val2 = sec_get(reql, reqr, 2*nowindex+2, (nowl+nowr)/2, nowr);
    return thisoperator(val1, val2);
   }
   void Printn(){
     cout<<"Printvector"<<endl;
     rep(i,n){
       cout<<nodes[i+n-1]<<" ";
     }
     cout<<endl;
   }
};
int main(void){
  ll n;
  cin>>n;
  string s;
  cin>>s;
  int q;
  cin>>q;
  vector<SegmentTree<int>> segs(26,SegmentTree<int>(n,0));
  rep(i,26){
    segs[i].initialize(n,0);
  }
  rep(i,n){
    segs[s[i]-'a'].update(i,1);
  }
  rep(i2,q){
    int mode;
    cin>>mode;
    if(mode==1){
      int i;
      char c;
      cin>>i>>c;
      i--;
      int old=s[i]-'a';
      segs[old].update(i,0);
      segs[c-'a'].update(i,1);
      s[i]=c;
    }else if(mode==2){
      int l,r;
      cin>>l>>r;
      l--;
      //r++;
      int ans=0;
      rep(j,26){
        if(segs[j].sec_get(l,r)>=1){
          ans++;
          //cout<<"find"<<" "<<j<<endl;
        }
      }
      cout<<ans<<endl;
    }
  }
  return 0;
}

//<<std::setprecision(30)

//重複削除
 /* std::sort(vec.begin(), vec.end());
  vec.erase(std::unique(vec.begin(), vec.end()), vec.end());*/


Measured memory_bytes: 142852