import java.util.*; import java.io.*; import java.math.*;
public class Main{
	static void solve(){//Here is the main function
      int N = nextInt();
      HashMap<String, TreeSet<Integer>> map = new HashMap<>();
      String[] slist = "abcdefghijklmnopqrstuvwxyz".split("");
      for(int i = 0; i < 26; i++){
        map.put(slist[i], new TreeSet<>());
      }
      ArrayList<String> s = nextCharArray();
      for(int i = 0; i < N; i++){
        TreeSet<Integer> count = map.get(s.get(i));
        count.add(i);
        map.put(s.get(i), count);
      }
      myerr(map);
      int Q = nextInt();
      for(int i = 0; i < Q; i++){
        ArrayList<String> tmp = nextStrArray();
        int no = Integer.parseInt(tmp.get(0));
        if(no == 1){
          int index = Integer.parseInt(tmp.get(1)) - 1;
          String ns = tmp.get(2);
          for(int j = 0; j < 26; j++){
            TreeSet<Integer> count = map.get(slist[j]);
            if(count.contains(index)){
              count.remove(index);
            }
            if(slist[j].equals(ns)){
              count.add(index);
            }
            map.put(slist[j], count);
          }
          //myerr(map);
        }else{
          int L = Integer.parseInt(tmp.get(1)) - 1;
          int R = Integer.parseInt(tmp.get(2)) - 1;
          int output = 0;
          for(int j = 0; j < 26; j++){
            TreeSet<Integer> count = map.get(slist[j]);
            Object Lc = count.ceiling(L);
            Object Rc = count.floor(R);
            if(Lc != null && Rc != null){
              int Lcc = (int)Lc;
              int Rcc = (int)Rc;
              if(Lcc <= R && Rcc >= L){
                output++;
              }
            }
          }
          myout(output);
        }
        
      }
	}
	//Method addition frame start



	//Method addition frame end

	//Don't have to see. start------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			try{
				while((read = br.readLine()) != null){
					inputLine.add(read);
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object t){System.err.print("debug:");System.err.println(t);}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextStrArray(){return myconv(next(), 8);}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<Integer> nextIntArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Integer> ret = new ArrayList<>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Integer.parseInt(input.get(i)));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Long> ret = new ArrayList<>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Long.parseLong(input.get(i)));
		}
		return ret;
	}
	static String myconv(Object list, int no){//only join
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof ArrayList){
			return String.join(joinString, (ArrayList)list);
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//Don't have to see. end------------------------------------------
}


Measured memory_bytes: 151288