#include<bits/stdc++.h>
using namespace std;using ll=long long;using vi=vector<int>;using vvi=vector<vi>;using vl=vector<ll>;using vvl=vector<vl>;using P=pair<int,int>;using PL=pair<ll,ll>;using vp=vector<P>;using vpl=vector<PL>;
#define pqueue priority_queue
template<typename T>constexpr auto inf=numeric_limits<T>::max()/2;constexpr int INF=inf<int>,MOD=1000000007;constexpr ll LINF=inf<ll>;
#define _ol3(_1,_2,_3,name,...)name
#define _rep(i,n)_repi(i,0,n)
#define _repi(i,a,b)for(int i=a,i##_l=(b);i<i##_l;++i)
#define REP(...)_ol3(__VA_ARGS__,_repi,_rep,)(__VA_ARGS__)
#define REPR(i,n)for(int i=n-1;i>=0;--i)
#define REPA(i,v)REP(i,(v).size())
#define all(v)(v).begin(),(v).end()
#define rall(v)(v).rbegin(),(v).rend()
#define bit(n)(1ll<<(n))
#define F first
#define S second
#define endl '\n'
#define cho(n,a,b)cout<<((n)?a:b)<<endl
void YES(int n){cho(n,"YES","NO");}void Yes(int n){cho(n,"Yes","No");}void Poss(int n){cho(n,"Possible","Impossible");}
void _print(ostream&){}template<class T,class...U>void _print(ostream&s,const T&t,const U&...u){s<<t<<(sizeof...(u)?' ':'\n');_print(s,u...);}
template<class...T>void print(const T&...t){_print(cout,t...);}template<class...T>void dprint(const T&...t){_print(cerr,t...);}
#ifndef LOCAL
struct osd{template<class T>osd&operator<<(const T&t){return*this;}};osd cer_;
#define dprint(...)
#define cerr cer_
#endif
#define dbg(x) dprint("@l",__LINE__,':',#x,'=',x)
template<class T>bool chmax(T&a,const T&b){bool x=a<b;x?a=b:b;return x;}template<class T>bool chmin(T&a,const T&b){bool x=a>b;x?a=b:b;return x;}
template<class T,class U>ostream&operator<<(ostream&o,const pair<T,U>&p){return o<<p.F<<' '<<p.S;}template<class T,class U>istream&operator>>(istream&i,pair<T,U>&p){return i>>p.F>>p.S;}
template<class T>class iterable{static false_type c(string v);template<class U>static auto c(U v)->decltype(all(v),true_type());static false_type c(...);public:const static bool value=decltype(c(declval<T>()))::value;};
template<class T,enable_if_t<iterable<T>::value,int> =0>ostream&operator<<(ostream&o,const T&v){for(auto&&i:v)o<<i<<' ';return o;}
template<class T>istream&operator>>(istream&i,vector<T>&v){for(T&j:v)i>>j;return i;}template<class T>vector<T>&operator<<(vector<T>&v,const T&t){v.push_back(t);return v;}
template<class T,class U>queue<T,U>&operator<<(queue<T,U>&v, const T&t){v.push(t);return v;}template<class T,class U>queue<T,U>&operator>>(queue<T,U>&v, T&t){t=v.front();v.pop();return v;}
template<class T,class U,class V>pqueue<T,U,V>&operator<<(pqueue<T,U,V>&v, const T&t){v.push(t);return v;}template<class T,class U,class V>pqueue<T,U,V>&operator>>(pqueue<T,U,V>&v, T&t){t=v.front();v.pop();return v;}
template<class T,class U>stack<T,U>&operator<<(stack<T,U>&v, const T&t){v.push(t);return v;}template<class T,class U>stack<T,U>&operator>>(stack<T,U>&v, T&t){t=v.front();v.pop();return v;}
template<class T,class U,class V>set<T,U,V>&operator<<(set<T,U,V>&v,const T&t){v.insert(t);return v;}template<class T,class U,class V>multiset<T,U,V>&operator<<(multiset<T,U,V>&v,const T&t){v.insert(t);return v;}
template<class T,enable_if_t<is_integral<T>::value,int> =0>T mod(T a, T b){if(a>0)return a%b;return b-(-a%b);}template<class T,enable_if_t<is_floating_point<T>::value,int> =0>T mod(T a, T b){if(a>0)return fmod(a,b);return b-fmod(-a,b);}
template<class T,class U>pair<T,U>&operator+=(pair<T,U>&a, pair<T,U>&b){a.F+=b.F;a.S+=b.S;return a;}template<class T,class U>pair<T,U>operator+(const pair<T,U>&a, const pair<T,U>&b){T r=a;return r+=b;}
template<class T,class U>pair<T,U>&operator-=(pair<T,U>&a, pair<T,U>&b){a.F-=b.F;a.S-=b.S;return a;}template<class T,class U>pair<T,U>operator-(const pair<T,U>&a, const pair<T,U>&b){T r=a;return r-=b;}
template<class T,class U>pair<T,U>operator-(const pair<T,U>&a){return mp(-a.F, -a.S);}
template<class T,class U>double std::norm(const pair<T,U>&p){return norm(p.F)+norm(p.S);}template<class T,class U>double std::abs(const pair<T,U>&p){return sqrt(norm(p));}

// thanks for: http://beet-aizu.hatenablog.com/entry/2017/12/01/225955
template <typename T,typename E>
struct SegmentTree{
  typedef function<T(T,T)> F;
  typedef function<T(T,E)> G;
  typedef function<E(E,E)> H;
  typedef function<E(E,int)> P;
  int n;
  F f;
  G g;
  H h;
  P p;
  T d1;
  E d0;
  vector<T> dat;
  vector<E> laz;
  SegmentTree(int n_,F f,G g,H h,T d1,E d0,
          vector<T> v=vector<T>(),P p=[](E a,int b){return a;}):
    f(f),g(g),h(h),d1(d1),d0(d0),p(p){
    init(n_);
    if(n_==(int)v.size()) build(n_,v);
  }
  void init(int n_){
    n=1;
    while(n<n_) n*=2;
    dat.clear();
    dat.resize(2*n-1,d1);
    laz.clear();
    laz.resize(2*n-1,d0);
  }
  void build(int n_, vector<T> v){
    for(int i=0;i<n_;i++) dat[i+n-1]=v[i];
    for(int i=n-2;i>=0;i--)
      dat[i]=f(dat[i*2+1],dat[i*2+2]);
  }
  inline void eval(int len,int k){
    if(laz[k]==d0) return;
    if(k*2+1<n*2-1){
      laz[k*2+1]=h(laz[k*2+1],laz[k]);
      laz[k*2+2]=h(laz[k*2+2],laz[k]);
    }
    dat[k]=g(dat[k],p(laz[k],len));
    laz[k]=d0;
  }
  T update(int a,int b,E x,int k,int l,int r){
    eval(r-l,k);
    if(r<=a||b<=l) return dat[k];
    if(a<=l&&r<=b){
      laz[k]=h(laz[k],x);
      return g(dat[k],p(laz[k],r-l));
    }
    return dat[k]=f(update(a,b,x,k*2+1,l,(l+r)/2),
        update(a,b,x,k*2+2,(l+r)/2,r));
  }
  T update(int a,int b,E x){
    return update(a,b,x,0,0,n);
  }
  T query(int a,int b,int k,int l,int r){
    eval(r-l,k);
    if(r<=a||b<=l) return d1;
    if(a<=l&&r<=b) return dat[k];
    T vl=query(a,b,k*2+1,l,(l+r)/2);
    T vr=query(a,b,k*2+2,(l+r)/2,r);
    return f(vl,vr);
  }
  T query(int a,int b){
    return query(a,b,0,0,n);
  }
};

int main(){
    cin.tie(0);ios::sync_with_stdio(0);
    cout<<setprecision(10);
    int n;
    string s;
    int q;
    cin>>n>>s>>q;
    auto add = [](int a, int b){return a+b;};
    vector<SegmentTree<int, int>> st;
    {
        REP(x,26){
            vi c(n);
            REP(i,n){
                c[i]=(s[i] == x+'a');
            }
            // dprint(c);
            st<<(SegmentTree<int, int>(n, add, add, add, 0, 0, c));
        }
    }
    REP(_,q){
        int t;
        int i;
        cin>>t>>i;
        --i;
        if(t==1){
            char c;
            cin>>c;
            dbg("a");
            dbg(s[i]);
            st[s[i]-'a'].update(i, i+1, -1);
            dbg("a");
            s[i]=c;
            st[s[i]-'a'].update(i, i+1, 1);
        }else{
            int r;
            cin>>r;
            --r;
            int c = 0;
            REP(j,26){
                if(st[j].query(i, r+1))++c;
            }
            cout<<c<<endl;
            dbg(c);
        }
    }
}


Measured memory_bytes: 291488