// Slower C++ solution:
#include <iostream>

#include <algorithm>

#include <array>

#include <bitset>

#include <cassert>

#include <cstring>

#include <deque>

#include <functional>

#include <initializer_list>

#include <math.h>

#include <map>

#include <random>

#include <set>

#include <stack>

#include <tuple>

#include <type_traits>

#include <queue>

#include <vector>





using lli = long long int;

using pii = std::pair<int, int>;



// グリッド上の縦横移動

constexpr std::array<std::pair<int, int>, 4> dxdy = {

    { {1, 0}, {-1, 0}, {0, 1}, {0, -1} }

};





template <typename T> inline bool chmin(T& a, T b){ if(b < a){ a = b; return true; } return false; }

template <typename T> inline bool chmax(T& a, T b){ if(a < b){ a = b; return true; } return false; }



inline bool isIn(int x, int y, int H, int W){return 0 <= x and x < H and 0 <= y and y < W;}

inline auto isInTheGrid(const int H, const int W){

    return std::bind(isIn, std::placeholders::_1, std::placeholders::_2, H, W);

}

inline bool bitUP(int state, int k){ return (state >> k) & 1; }

inline bool bitUP(long long int state, int k){ return (state >> k) & 1;}





namespace MyInputAndOutput{

    // 入力関係 (cin)

    class user_input{

    public:

        inline const user_input& operator >> (int& int_arg) const {

            scanf("%d", &int_arg); return *this;

        }

        inline const user_input& operator >> (long long int& llint_arg) const {

            scanf("%lld", &llint_arg); return *this;

        }

        inline const user_input& operator >> (unsigned int& uint_arg) const {

            scanf("%u", &uint_arg); return *this;

        }

        inline const user_input& operator >> (unsigned long long int& ullint_arg) const {

            scanf("%llu", &ullint_arg); return *this;

        }

        inline const user_input& operator >> (unsigned long& ullint_arg) const {

            scanf("%lu", &ullint_arg); return *this;

        }

        inline const user_input& operator >> (char* str_arg) const {

            scanf("%s", str_arg); return *this;

        }

        inline const user_input& operator >> (char& char_arg) const {

            scanf("%*c%c", &char_arg); return *this;

        }

        template <typename S, typename T>

        inline const user_input& operator >>(std::pair<S, T>& pair_arg) const{

            (*this) >> pair_arg.first >> pair_arg.second; return *this;

        }

        template <typename T>

        inline const user_input& operator >>(std::vector<T>& vec) const {

            for(T& ele : vec) (*this) >> ele; return *this;

        }

    } cin;



    void ends(void) {putchar('\0'); }

    void endl(void) {putchar('\n'); fflush(stdout);}

    void flush(void) {fflush(stdout);}



    // 出力関係 (cout)

    class user_output{

    public:

        user_output(void){}

        inline const user_output& operator << (const int int_arg) const{

            printf("%d", int_arg); return *this;

        }

        inline const user_output& operator << (const unsigned int uint_arg) const{

            printf("%u", uint_arg); return *this;

        }

        inline const user_output& operator << (const long long int llint_arg) const {

            printf("%lld", llint_arg); return *this;

        }

        inline const user_output& operator << (const unsigned long long int ullint_arg) const {

            printf("%llu", ullint_arg); return *this;

        }

        inline const user_output& operator << (const unsigned long ulint_arg) const {

            printf("%lu", ulint_arg); return *this;

        }

        inline const user_output& operator << (const double ld_arg) const {

            printf("%.16lf", ld_arg); return *this;

        }

        inline const user_output& operator << (const long double ld_arg) const {

            printf("%.16Lf", ld_arg); return *this;

        }

        inline const user_output& operator << (const char char_arg) const {

            putchar(char_arg); return *this;

        }

        inline const user_output& operator << (const unsigned char uchar_arg) const {

            putchar(uchar_arg); return *this;

        }

        inline const user_output& operator << (const char* str_arg) const {

            fputs(str_arg, stdout); return *this;

        }

        inline const user_output& operator << (void(* const func_arg)(void)) const {

            func_arg(); return *this;

        }

        template <typename S, typename T>

        inline const user_output& operator <<(const std::pair<S, T>& pair_arg) const{

            (*this) << pair_arg.first << ' ' << pair_arg.second; return *this;

        }

        template <typename Tp_name>

        inline const user_output& operator << (const std::vector<Tp_name>& vec) const {

            const size_t size_of_vec = vec.size();

            if(size_of_vec <= 0) return *this;

            (*this) << vec[0]; 

            for(size_t index = 1; index < size_of_vec; ++index) (*this) << ' ' << vec[index];

            return *this;

        }

    } cout;



    // その他出力関数

    void binary_output(int64_t value, size_t length = 64){

        char out[length + 1];

        for(size_t i = 0; i < length; ++i) out[length - 1 - i] = ((value >> i) & 1) ? '1' : '0';

        out[length] = '\0'; puts(out);

    }

    template <typename InputType>

    void print(InputType first, InputType last, const char separate_c = ' ', const char end_c = '\n'){

        InputType it = first;

        while(true){

            MyInputAndOutput::cout << *it;

            if(++it == last){MyInputAndOutput::cout << end_c; return;}

            MyInputAndOutput::cout << separate_c;  

        }

    }

}; namespace MIO = MyInputAndOutput;



// z-algorithm

template <class T> std::vector<int> z_algorithm(const T &str) {

    const size_t n = str.size();

    std::vector<int> resOfCP(n); resOfCP[0] = n;

    int i = 1, j = 0;

    while (i < n) {

        while (i + j < n and str[j] == str[i + j]) ++j;

        resOfCP[i] = j;

        if (j == 0) { ++i; continue;}

        int k = 1;

        while (i + k < n and k + resOfCP[k] < j) resOfCP[i + k] = resOfCP[k], ++k;

        i += k; j -= k;

    }

    return resOfCP;

} 







// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~





class SegmentTree{

private:

    int n; // 配列の大きさ

    int N; // 2の冪乗

    std::vector<int> data; // データを格納する配列

public:

    SegmentTree(int n = 0):n(n){

        N = 1; while(N < n) N <<= 1;

        data.assign(2 * N, 0);

    }

    void resize(int nn){

        n = nn; N = 1; while(N < n) N <<= 1;

        data.assign(2 * N, 0);

    }

     // 作用素 opで, A[idx]の値を更新

    void update(int idx, int op){

        idx += N;

        data[idx] += op;

        idx /= 2;

        while(idx > 0){

            data[idx] = data[2 * idx] + data[2 * idx + 1];

            idx /= 2;

        }

    }

    // 区間 [l, r) での値を取得

    int query(int l, int r)const{

        int res = 0;

        l += N; r += N;

        while(l < r){

            if(l & 1) res += data[l++];

            if(r & 1) res += data[--r];

            l >>= 1; r >>= 1;

        }

        return res;

    }

    int at(int idx){

        return data[idx + N];

    }

};











constexpr int ALPHA_SIZE = 'z' - 'a' + 1;

constexpr unsigned int N = 5e5;

char S[N + 10];

using datum = std::tuple<bool, int, int>;

std::vector<datum> query;

std::vector<int> SC[ALPHA_SIZE];

SegmentTree ST[ALPHA_SIZE];



int main(void){

    int n, q; MIO::cin >> n >> S >> q;

    for(int i = 0; i < ALPHA_SIZE; ++i){ SC[i].resize(n+1); SC[i][0] = 0;}

    for(int i = 0; i < n; ++i){

        for(int j = 0; j < ALPHA_SIZE; ++j) SC[j][i+1] = SC[j][i]; 

        SC[S[i] - 'a'][i+1]++;

    }



    query.resize(q);



    std::vector<int> D; D.reserve(2 * q);

    for(int i = 0; i < q; ++i){

        char c; MIO::cin >> c;

        if(c == '1'){

            int idx; char d; MIO::cin >> idx >> d; idx--;

            query[i] = {true, idx, d};

            D.push_back(idx);

        }

        else{

            int l, r; MIO::cin >> l >> r; l--;

            query[i] = {false, l, r};

            D.push_back(l); D.push_back(r);

        }

    }

    std::sort(D.begin(), D.end());

    D.erase(std::unique(D.begin(), D.end()), D.end());



    const int sz = D.size();

    for(int j = 0; j < ALPHA_SIZE; ++j) ST[j].resize(sz);



    for(int i = 0; i < q; ++i){

        bool f; int l, r; std::tie(f, l, r) = query[i];

        if(f){

            char c = r;

            if(S[l] == c) continue;

            int ptr = std::lower_bound(D.begin(), D.end(), l) - D.begin();

            ST[S[l] - 'a'].update(ptr, -1);

            S[l] = c;

            ST[S[l] - 'a'].update(ptr, 1);

        }

        else{

            int cnt = 0;

            for(int j = 0; j < ALPHA_SIZE; ++j){

                int C = SC[j][r] - SC[j][l];

                int l1 = std::lower_bound(D.begin(), D.end(), l) - D.begin();

                int r1 = std::lower_bound(D.begin(), D.end(), r) - D.begin();

                C += ST[j].query(l1, r1);

                //MIO::cout << char(j + 'a') << " : " << C << ' ' << ST[j].query(l1, r1) << '\n';

                if(C > 0) cnt++;

            }

            MIO::cout << cnt << '\n';

        }

    }











    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.077501074082813x):
#include <stdio.h>



constexpr char* S_OUT[31] = {

    "0\n", "1\n", "2\n", "3\n", "4\n", "5\n", "6\n", "7\n", "8\n", "9\n", "10\n",

    "11\n", "12\n", "13\n", "14\n", "15\n", "16\n", "17\n", "18\n", "19\n", "20\n",

    "21\n", "22\n", "23\n", "24\n", "25\n", "26\n", "27\n", "28\n", "29\n", "30\n"

};



constexpr unsigned int InputSize = 3e6;

constexpr unsigned int OutputSize = 3e5;

char Input[InputSize];

char* pointer = Input;

char Output[OutputSize];

char* m_buffer = Output;



inline unsigned int getInt(void){

    unsigned int res = 0;

    do{ res = 10 * res + (*(pointer++) - '0'); } while(*pointer >= '0');

    return res;

}



inline void out(int v){

    char* str = S_OUT[v];

    while(*str) *(m_buffer++) = *(str++);

}



unsigned int n;

unsigned int N;

constexpr unsigned int SIZE = (1U << 19) + 1;

unsigned int data[2 * SIZE];



inline void set(void){

    n = getInt(); N = 1U << (31 - __builtin_clz(n)); while(N < n) N <<= 1;

    ++pointer; // \n

    unsigned int i, j;

    for(i = 0, j = N; i < n; ++i, ++j) data[j] = 1U << (*(pointer++) - 'a');

    for(i = N - 1; i ; --i) data[i] = data[i << 1] | data[(i << 1) | 1U];

}



inline void query(void){

    pointer += 3;

    if(*(pointer - 2) == '1'){

        unsigned int index = getInt() - 1;

        unsigned char idx = *((++pointer)++) - 'a';

        data[index += N] = 1U << idx;

        while(index >>= 1) data[index] = data[index << 1] | data[(index << 1) | 1U];

    }

    else{

        unsigned int l = getInt() + N - 1; pointer++;

        unsigned int r = getInt() + N;

        unsigned int res = 0;

        while(l < r){

            if(l & 1) res |= data[l++]; l >>= 1;

            if(r & 1) res |= data[--r]; r >>= 1;

        }

        out(__builtin_popcount(res));

    }

}



int main(void){

    fread(Input, sizeof(char), InputSize, stdin);

    set(); ++pointer;

    unsigned int q = getInt();

    while(q--) query();

    setvbuf(stdout, 0, _IONBF, 0);

    fputs(Output, stdout);

    return 0;

}