#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define REPR(i,n) for (int i=(int)(n)-1;i>=0;--i)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
#define ALL(c) (c).begin(), (c).end()
#define valid(y,x,h,w) (0<=y&&y<h&&0<=x&&x<w)
#define tpl(...) make_tuple(__VA_ARGS__)
const int INF = 0x3f3f3f3f;
const double EPS = 1e-8;
const double PI = acos(-1);
const int dy[] = {-1,0,1,0};
const int dx[] = {0,1,0,-1};
typedef long long ll;
typedef pair<int,int> pii;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename Ch,typename Tr,typename C,typename=decltype(begin(C()))>basic_ostream<Ch,Tr>& operator<<(basic_ostream<Ch,Tr>&os,
const C& c){os<<'[';for(auto i=begin(c);i!=end(c);++i)os<<(i==begin(c)?"":" ")<<*i;return os<<']';}
template<class S,class T>ostream&operator<<(ostream &o,const pair<S,T>&t){return o<<'('<<t.first<<','<<t.second<<')';}
template<int N,class Tp>void output(ostream&,const Tp&){}
template<int N,class Tp,class,class ...Ts>void output(ostream &o,const Tp&t){if(N)o<<',';o<<get<N>(t);output<N+1,Tp,Ts...>(o,t);}
template<class ...Ts>ostream&operator<<(ostream&o,const tuple<Ts...>&t){o<<'(';output<0,tuple<Ts...>,Ts...>(o,t);return o<<')';}
template<class T>void output(T t,char z=10){if(t<0)t=-t,putchar(45);int c[20];
int k=0;while(t)c[k++]=t%10,t/=10;for(k||(c[k++]=0);k;)putchar(c[--k]^48);putchar(z);}
template<class T>void outputs(T t){output(t);}
template<class S,class ...T>void outputs(S a,T...t){output(a,32);outputs(t...);}
template<class T>void output(T *a,int n){REP(i,n)cout<<a[i]<<(i!=n-1?',':'\n');}
template<class T>void output(T *a,int n,int m){REP(i,n)output(a[i],m);}
template<class T>bool input(T &t){int n=1,c;for(t=0;!isdigit(c=getchar())&&~c&&c-45;);
if(!~c)return 0;for(c-45&&(n=0,t=c^48);isdigit(c=getchar());)t=10*t+c-48;t=n?-t:t;return 1;}
template<class S,class ...T>bool input(S&a,T&...t){input(a);return input(t...);}
template<class T>bool inputs(T *a, int n) { REP(i,n) if(!input(a[i])) return 0; return 1;}

template<class T, int MAX_N>
struct BIT {
  int N, K; T B[MAX_N];
  void init(int n) {N=n;REP(i,n)B[i]=0;for(K=1;(K<<1)<N;K<<=1);}
  void add(int x, T w) { for (; x<N; x|=x+1) B[x]+=w; }
  T sum(int a) const { T r=0; for (int x=a-1; x>=0; x=(x&(x+1))-1) r+=B[x]; return r; }
  T sum(int a, int b) const { return sum(b)-sum(a); }
  int lb(T w) { int x=0; for(int k=K; k; k>>=1) if (x+k<=N && B[x+k-1]<w) w-=B[x+k-1], x+=k; return x; }
  friend ostream& operator<<(ostream&o, const BIT<T, MAX_N> &bit) {  REP(i,bit.N) o << (i?",":"") << bit.sum(i, i+1); o << endl; return o; }
};

BIT<int, 1000000> bit[26];

int main() {
  int n;
  while(cin>>n) {
    REP(i,26) {
      bit[i].init(n);
    }
    string s;
    cin >> s;
    REP(i,n) {
      bit[s[i]-'a'].add(i,1);
    }
    int Q;
    cin>> Q;
    while(Q--) {
      int x;
      input(x);
      if (x == 1) {
        int i;
        char c;
        scanf("%d %c", &i, &c);
        i--;
        bit[s[i]-'a'].add(i,-1);
        bit[c-'a'].add(i,1);
        s[i] = c;
      } else {
        int l,r;
        input(l,r);
        l--;
        int ans = 0;
        REP(i,26) if (bit[i].sum(l,r) > 0) ans++;
        printf("%d\n", ans);
      }
    }
  }
}


Measured memory_bytes: 101252