#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> bool mmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool mmin(T &m, const T q) { if (q < m) {m = q; return true;} else return false; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;

// Nonrecursive Segment Tree (point-update, range-get)
// - Conditions for operations:
//   - datamerge: [TDATA, TDATA] -> TDATA, e(x, y) == e(y, x)
//   - data2ret: [TDATA, TQUERY] -> TRET
//   - retmerge: [TRET, TRET] -> TRET, g(defaultRET, x) == x, g(x, y) = g(y, x)
//   - commutability f(e(x, y), q) == g(f(x, q), f(y, q))
template<typename TDATA, typename TRET, typename TQUERY>
struct NonrecursiveSegmentTree
{
    int N;
    TRET defaultRET;
    virtual TDATA datamerge(const TDATA &, const TDATA &) = 0;
    virtual TRET data2ret(const TDATA &, const TQUERY &) = 0;
    virtual TRET retmerge(const TRET &, const TRET &) = 0;
    std::vector<TDATA> data;
    inline TDATA& at(int i) { return data[i]; }

    inline void _merge(int i) { at(i) = datamerge(at(i << 1), at((i << 1) + 1)); }
    void initialize(const std::vector<TDATA> &seq, TRET RET_ZERO) {
        N = seq.size();
        defaultRET = RET_ZERO;
        data = seq;
        data.insert(data.end(), seq.begin(), seq.end());
        for (int i = N - 1; i; i--) _merge(i);
    }
    NonrecursiveSegmentTree() = default;
    void update(int pos, const TDATA &x) {
        assert(pos >= 0 and pos < N);
        at(pos + N) = x;
        for (int i = pos + N; i > 1;) i >>= 1, _merge(i);
    }

    // [l, r), 0-indexed
    TRET get(int l, int r, TQUERY query = NULL) {
        assert(l >= 0 and r <= N);
        TRET retl = defaultRET, retr = defaultRET;
        l += N, r += N;
        while (l < r) {
            if (l & 1) retl = retmerge(retl, data2ret(data[l++], query));
            if (r & 1) retr = retmerge(data2ret(data[--r], query), retr);
            l >>= 1, r >>= 1;
        }
        return retmerge(retl, retr);
    }

    template<typename T1, typename T2, typename T3>
    friend std::ostream &operator<<(std::ostream &os, NonrecursiveSegmentTree<T1, T2, T3> s) {
        os << "[SegmentTree (len: " << s.N << ')';
        for (int i = 0; i < s.N; i++) os << s.at(i + s.N) << ',';
        os << "]";
        return os;
    }
};


// Range Minimum Query
// - get: return min(x_l, ..., x_{r - 1})
using T = int;
struct RangeOrQuery : public NonrecursiveSegmentTree<T, T, bool>
{
    using SegTree = NonrecursiveSegmentTree<T, T, bool>;
    T datamerge(const T &vl, const T &vr) override { return vl | vr; };
    T data2ret(const T &v, const bool &q) override { return v; }
    T retmerge(const T &vl, const T &vr) override { return vl | vr; };
    RangeOrQuery(const std::vector<T> &seq, T defaultmin) : SegTree::NonrecursiveSegmentTree() {
        SegTree::initialize(seq, defaultmin);
    };
};

int main()
{
    int N;
    string S;
    cin >> N >> S;
    vector<int> v(N);
    REP(i, N) v[i] = 1 << (S[i] - 'a');
    RangeOrQuery segtree(v, 0);

    int Q;
    cin >> Q;
    while (Q--)
    {
        int q;
        cin >> q;
        if (q == 1) {
            int i;
            char c;
            cin >> i >> c;
            segtree.update(i - 1, 1 << (c - 'a'));
        }
        else {
            int l, r;
            cin >> l >> r;
            int ret = segtree.get(l - 1, r);
            printf("%d\n", __builtin_popcount(ret));
        }
    }
}


Measured memory_bytes: 8732