#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <array>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
#include <bitset>
#include <tuple>
#include <cmath>
#include <complex>
#include <algorithm>
#include <utility>
#include <regex>
#include <cstdint>
#include <numeric>
#include <functional>
#include <cassert>

using namespace std;
using ll  = long long;
using ull = unsigned long long;

namespace utils{
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
    template<class T, class Compare> using p_queue = priority_queue<T, vector<T>, Compare>;
    template<class T> using min_queue = p_queue<T, greater<T>>;
    template<class T> using max_queue = p_queue<T, less<T>>;

    template<class T> inline bool UPMIN(T& X, const T& A){ if(X > A) {X = A; return true;} return false; }
    template<class T> inline bool UPMAX(T& X, const T& A){ if(X < A) {X = A; return true;} return false; }

    template<class T>
    vector<T> VEC(int n, T t){
        return vector<T>(n, t);
    }
    template<class ...Ts>
    auto VEC(int n, Ts ... ts){
        return vector<decltype(VEC(ts...))>(n, VEC(ts...));
    }

    template <class S, class T>
    istream& operator>>(istream& is, tuple<S, T>& t){
        return is >> get<0>(t) >> get<1>(t);
    }

    template <class S, class T, class U>
    istream& operator>>(istream& is, tuple<S, T, U>& t){
        return is >> get<0>(t) >> get<1>(t) >> get<2>(t);
    }

    template <class S, class T>
    ostream& operator<<(ostream& os, const tuple<S, T>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t);
    }

    template <class S, class T, class U>
    ostream& operator<<(ostream& os, const tuple<S, T, U>& t){
        return os << get<0>(t) << ' ' <<  get<1>(t) << ' ' <<  get<2>(t);
    }

    template<class T>
    istream& operator>>(istream& is, vector<T>& v){
        for (auto &&x : v) { is >> x; } return is;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<T>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << ' ' << *p++;
        }
        return os ;
    }

    template<class T>
    ostream& operator<<(ostream& os, const vector<vector<T>>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << '\n' << *p++;
        }
        return os;
    }

    template<class ...Ts>
    ostream& operator<<(ostream& os, const vector<tuple<Ts...>>& v){
        auto p = v.begin();
        assert(p != v.end());
        os << *p++;
        while(p != v.end()){
            os << '\n' << *p++;
        }
        return os;
    }

    constexpr long long INFLL   = 1'000'000'000'000'000'000ll;
    constexpr int       INF     = 1'000'000'000;
    constexpr double    PI      = 3.14'159'265'358'973;
    constexpr double    EPS     = 1e-10;
}
using namespace utils;

template<class Monoid>
class SegmentTree {
    using Func = std::function<Monoid(Monoid, Monoid)>;
    int N;

    std::vector<Monoid> segment;

    const Func op;
    const Monoid id;

    bool dirty_flag;
public:
    // id : op = max なら -INT_MAX
    SegmentTree(int n, const Func biop, const Monoid& M1)
    : op(biop), id(M1), dirty_flag(false) {
        N = 1;
        while(N < n) N *= 2;
        segment.assign(2 * N, id);
    }

    void set(int k, const Monoid &a){
        dirty_flag = true;
        segment[k + N] = a;
    }

    void build() {
        for (int k = N - 1; k > 0; --k) {
            segment[k] = op(segment[2 * k], segment[2 * k + 1]);
        } // end k
        dirty_flag = false;
    }

    void update(int k, const Monoid& a){
        k += N;
        segment[k] = a;
        while(k /= 2){
            segment[k] = op(segment[k*2], segment[k*2+1]);
        }
    }

    // -> op [a,b)
    Monoid query(unsigned a, unsigned b){
        if(dirty_flag) build();
        dirty_flag = false;
        Monoid L = id, R = id;
        for (a += N, b += N; a < b; a >>= 1u, b >>= 1u) {
            if(a & 1u) L = op(L, segment[a++]);
            if(b & 1u) R = op(segment[--b], R);
        } // end i
        return op(L, R);
    }

    Monoid operator[](const int &k) const{
        return segment[k + N];
    }
};


class solver{
    istream& is;
    ostream& os;

public:
    solver(istream& I, ostream& O) :is(I), os(O) {}

    int N, Q;
    string S;
    bool input() {
        is >> N >> S >> Q;
        return !!is;
    }

    void run();
};

int main(int argc, char *argv[]) {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(16) << scientific;
#ifdef XELMH
    string test_cases = "test_B.txt";
    cerr << test_cases << " -->" << endl;
    auto fs = fstream(test_cases, fstream::in);
    int loop = 0;
    while(fs) {
        loop++;
        cout << '#' << loop << "#------\n";
        solver(fs, cout).run();
    }
    if(loop <= 1) {
        cout << "===" << endl;
        while(cin) solver(cin, cout).run();
    }
#else
    solver(cin, cout).run();
#endif
    return 0;
}


void solver::run(){
    if(!input()) return;
    using alset = bitset<30>;
    SegmentTree<alset> seg(N, [](alset a, alset b){
        return a | b;
    }, 0);

    vector<alset> als;
    als.reserve('z' - 'a'+1);
    for (int al = 0; al < 'z' - 'a'+1; ++al) {
        als.emplace_back(1<<al);
    } // end al

    for (int i = 0; i < N; ++i) {
        seg.set(i, als[S[i]-'a']);
    } // end i

    for (int i = 0; i < Q; ++i) {
        int q;
        is >> q;
        if(q == 1){
            int x; char c;
            is >> x >> c;
            seg.update(x-1, als[c-'a']);
        }
        else {
            int l, r;
            is >> l >> r;
            auto an = seg.query(l-1, r);
            os << an.count() << endl;
        }
    } // end i

}


Measured memory_bytes: 9116