#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <numeric>
#include <utility>
#include <tuple>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
using ll = long long int;
using P = pair<int, int>;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; PPPPP(__VA_ARGS__); cerr << endl; } while(false)
template<typename T> void PPPPP(T t) { cerr << t; }
template<typename T, typename... S> void PPPPP(T t, S... s) { cerr << t << ", "; PPPPP(s...); }
#else
#define dump(...) do{ } while(false)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T> bool chmin(T &a, T b) { if (a > b) {a = b; return true; } return false; }
template<typename T> bool chmax(T &a, T b) { if (a < b) {a = b; return true; } return false; }
template<typename T> void print(T a) { cout << a << endl; }
template<typename T, typename... Ts> void print(T a, Ts... ts) { cout << a << ' '; print(ts...); }
template<typename T> istream &operator,(istream &in, T &t) { return in >> t; }
// clang-format on

#include <functional>
template<typename T>
class SegmentTreeOneAll {
    using Func = function<T(T, T)>;

public:
    vector<T> data;
    int n;
    T init;
    Func update_func;
    Func query_func;
    SegmentTreeOneAll(int _n, T _init, Func up, Func qu) {
        init = _init;
        update_func = up;
        query_func = qu;
        for (n = 1; n < _n; n *= 2)
            ;
        data.resize(2 * n - 1, init);
    }
    void update(int pos, T val) {
        pos += n - 1;
        data[pos] = update_func(data[pos], val);
        while (pos > 0) {
            pos = (pos - 1) / 2;
            data[pos] = query_func(data[2 * pos + 1], data[2 * pos + 2]);
        }
    }
    T query(int l, int r) {
        T resL = init, resR = init;
        for (l += n - 1, r += n - 1; l < r; l = l / 2, r = (r - 1) / 2) {
            if (!(l & 1)) {
                resL = query_func(resL, data[l]);
            }
            if (!(r & 1)) {
                resR = query_func(data[r - 1], resR);
            }
        }
        return query_func(resL, resR);
    }
};

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n, q;
    string s;
    cin, n, s, q;

    auto UPDATE = [](int a, int b) {
        return b;
    };
    auto OR = [](int a, int b) {
        return a | b;
    };
    SegmentTreeOneAll<int> seg(n, 0, UPDATE, OR);
    REP(i, 0, n) {
        seg.update(i, 1 << (s[i] - 'a'));
    }

    REP(_, 0, q) {
        int t;
        cin, t;
        if (t == 1) {
            int ind;
            char c;
            cin, ind, c;
            seg.update(ind - 1, 1 << (c - 'a'));
        } else {
            int l, r;
            cin, l, r;
            int res = seg.query(l - 1, r);
            int cnt = 0;
            while (res) {
                cnt += res % 2;
                res >>= 1;
            }
            cout << cnt << endl;
        }
    }
    return 0;
}


Measured memory_bytes: 5148