#include <bits/stdc++.h>

using namespace std;

#define DUMP(x) std::cerr << (#x) << " = " << (x) << "\n"
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define REP(i, k, n) for (int i = (k); i < (int)(n); ++i)
#define ALL(r) r.begin(), r.end()
#define YES cout << "YES" << endl
#define Yes cout << "Yes" << endl
#define NO cout << "NO" << endl
#define No cout << "No" << endl
#define IMP cout << "IMPOSSIBLE" << endl
#define Imp cout << "Impossible" << endl
#define imp cout << "impossible" << endl
#define M1 cout << "-1" << endl
#define pb push_back
#define eb emplace_back
#define fi first
#define se second

template <typename T>
ostream &operator<<(ostream &os, vector<T> &v)
{
    os << "{";
    rep(i, v.size()) os << v[i] << (i == (int)v.size() - 1 ? "" : ", ");
    os << "}";
    return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &p)
{
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}
template <typename T>
T dup(T x, T y)
{
    return (x + y - 1) / y;
};
template <typename A, size_t N, typename T>
inline void arrayFill(A (&array)[N], const T &val) { std::fill((T *)array, (T *)(array + N), val); }
struct in
{
    const size_t n = 0;
    in() = default;
    in(size_t n) : n(n){};
    template <typename T>
    operator T()
    {
        T ret;
        cin >> ret;
        return ret;
    }
    template <typename T>
    operator vector<T>()
    {
        assert(n != 0);
        vector<T> ret(n);
        for (auto &x : ret)
            cin >> x;
        return ret;
    }
};

using ll = int64_t;
using vint = vector<int32_t>;
using vvint = vector<vint>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vstr = vector<string>;
using pint = pair<int32_t, int32_t>;
using vpint = vector<pint>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using setint = set<int32_t>;
using setstr = set<string>;
using qint = queue<int32_t>;
using qpint = queue<pint>;

constexpr std::int32_t INF = 1001001001;
constexpr std::int64_t LINF = 1001001001001001001;

template <typename T>
struct SegmentTree
{
    using F = function<T(T, T)>;
    int n;
    F f;
    T ti;
    vector<T> dat;

    SegmentTree() {}
    SegmentTree(F f, T ti) : f(f), ti(ti) {}

    void init(int n_)
    {
        n = 1;
        while (n < n_)
            n <<= 1;
        dat.assign(n << 1, ti);
    }

    void build(const vector<T> &v)
    {
        int n_ = v.size();
        init(n_);
        for (int i = 0; i < n_; i++)
            dat[n + i] = v[i];
        for (int i = n - 1; i; i--)
            dat[i] = f(dat[(i << 1) | 0], dat[(i << 1) | 1]);
    }

    void set_val(int k, T x)
    {
        dat[k += n] = x;
        while (k >>= 1)
            dat[k] = f(dat[(k << 1) | 0], dat[(k << 1) | 1]);
    }

    T query(int a, int b)
    {
        if (a >= b)
            return ti;
        T vl = ti, vr = ti;
        for (int l = a + n, r = b + n; l < r; l >>= 1, r >>= 1)
        {
            if (l & 1)
                vl = f(vl, dat[l++]);
            if (r & 1)
                vr = f(dat[--r], vr);
        }
        return f(vl, vr);
    }
};
constexpr int N = 256;

void Main()
{
    int n = in();
    string s = in();
    int q = in();

    // 演算
    auto f = [](int a, int b) { return a | b; };
    // 単位元
    int ti = 0;
    // 初期化
    SegmentTree<int> seg(f, ti);

    // セグ木を構築
    vector<int> v(n, ti);
    rep(i, n)
    {
        v[i] = (1 << (s[i] - 'a'));
    }
    seg.build(v);

    rep(_, q)
    {
        int t = in();
        if (t == 1)
        {
            int i = in();
            --i;
            char c = in();
            seg.set_val(i, (1 << (c - 'a')));
        }
        else
        {
            int l = in(), r = in();
            --l, --r;
            cout << __builtin_popcount(seg.query(l, r + 1)) << endl;
        }
    }
}

signed main()
{
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << std::fixed << std::setprecision(15);
    Main();
    return 0;
}


Measured memory_bytes: 7068