#include <bits/stdc++.h>
#define range(i, l, r) for(long long int (i) = (l); (i) < (r); (i)++)
#define reversed_range(i, l, r) for (long long int (i) = (r) - 1; (i) >= l; (i)--)
using namespace std;
template <typename T>
using vec = vector<T>;
using lint = long long;
using ulint = unsigned long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;

template <typename S, typename T>
ostream& operator <<(ostream& os, pair<S, T> p) {
    os << "(";
    os << p.first << ", " << p.second;
    return os << ")";
}

template <typename T>
ostream& operator <<(ostream& os, vec<T> v) {
    os << "[";
    if (v.size() == 0) return os << "]";
    for (int i = 0; i < v.size() - 1; i++) {
        os << v.at(i) << ", ";
    }
    return os << v.at(v.size() - 1) << "]";
}

template <typename T>
ostream& operator <<(ostream& os, set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    os << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        os << ", " << *it;
    }
    return os << "}";
}

template <typename T>
ostream& operator <<(ostream& os, unordered_set<T>& s) {
    os << "{";
    if (s.begin() == s.end()) return os << "}";
    auto it_first_item = s.begin();
    os << *it_first_item;
    for (auto it = ++it_first_item; it != s.end(); it++) {
        os << ", " << *it;
    }
    return os << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    os << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        os << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

template <typename K, typename V>
ostream& operator <<(ostream& os, unordered_map<K, V> m) {
    os << "{";
    if (m.begin() == m.end()) return os << "}";
    auto it_first_item = m.begin();
    os << it_first_item->first << ": " << it_first_item->second;
    for (auto it = ++it_first_item; it != m.end(); it++) {
        os << ", " << it->first << ": " << it->second;
    }
    return os << "}";
}

lint pow(lint num, lint e, lint MOD) {
    lint res = 1;
    lint cur_num = num;
    while (e) {
        if (e & 1) {
            res *= cur_num;
            res %= MOD;
        }
        cur_num *= cur_num;
        cur_num %= MOD;
        e >>= 1;
    }
    return res;
}

void add_value_to(vec<lint>& bit, lint idx, lint val) {
    while (idx < bit.size()) {
        bit.at(idx) += val;
        idx += idx & -idx;
    }
}

lint sum(vec<lint>& bit, lint idx) {
    lint ans = 0;
    while (idx > 0) {
        ans += bit.at(idx);
        idx -= idx & -idx;
    }
    return ans;
}

int main() {
    cin.tie(0); cout.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    lint N, Q; string S;
    cin >> N >> S >> Q;
    vec<vec<lint>> bit_list(26, vec<lint>(2 * N + 10, 0));
    range(i, 0, N) {
        char c = S.at(i);
        add_value_to(bit_list.at(c - 'a'), i + 1, 1);
    }
    range(_, 0, Q) {
        lint t; cin >> t;
        if (t == 1) {
            lint i; char c;
            cin >> i >> c;
            add_value_to(bit_list.at(S.at(i - 1) - 'a'), i, -1);
            add_value_to(bit_list.at(c - 'a'), i, 1);
            S.at(i - 1) = c;
        } else {
            lint l, r; cin >> l >> r;
            lint ans = 0;
            range(i, 0, 26) {
                lint num_appeared = sum(bit_list.at(i), r);
                if (l > 1) num_appeared -= sum(bit_list.at(i), l - 1);
                ans += num_appeared > 0;
            }
            cout << ans << "\n";
        }
    }
}

Measured memory_bytes: 211868