#include<iostream>
#include<functional>
#include<vector>
#include<string>
#define rep(i, start, end) for (int i = (int)start; i < (int)end; ++i)
#define rrep(i, start, end) for (int i = (int)start - 1; i >= end; --i)
#define iter(i, c) for (auto i = (c).begin(); i != (c).end(); ++i)
#define riter(i, c) for (auto i = (c).rbegin(); i != (c).rend(); ++i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using namespace std;
using ll = long long;
template<typename T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return 0;}
template<typename T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return 0;}

template <typename T>
class SegTree {
    private:
        size_t node_size_;
        vector<T> node_;
        T identity_;                     // ex) INF, 0, etc...
        function<T(T, T)> operation_;    // ex) min, max, sum, etc...
        function<T(T, T)> update_;       // ex) add, change, etc..
    public:
        SegTree(size_t node_size, T identity, function<T(T, T)> operation, function<T(T, T)> update):
        identity_(identity), operation_(operation), update_(update) {
            node_size_ = 1;
            while (node_size_ < node_size) node_size_ *= 2;
            node_ = vector<T>(2 * node_size_ - 1, identity);
        }
        void change(int idx, T new_value) {
            int node_idx = idx + node_size_ - 1;
            node_[node_idx] = update_(node_[node_idx], new_value);
            while (node_idx > 0) {
                node_idx = (node_idx - 1) / 2;
                node_[node_idx] = operation_(node_[node_idx * 2 + 1], node_[node_idx * 2 + 2]);
            }
        }
        T _query(int left, int right, int node_idx, int node_left, int node_right) {
            if (node_right <= left || right <= node_left) {
                return identity_;
            }
            if (left <= node_left && node_right <= right) {
                return node_[node_idx];
            }
            else {
                T left_value = _query(left, right, node_idx * 2 + 1, node_left, (node_left + node_right) / 2);
                T right_value = _query(left, right, node_idx * 2 + 2, (node_left + node_right) / 2, node_right);
                return operation_(left_value, right_value);
            }
        }
        T query(int left, int right) {
            return _query(left, right, 0, 0, node_size_);
        }
        T operator[](int idx) {
            return node_[idx + node_size_ - 1];
        }
        // serach-method's usage is written on CF567
        int _search(int kth, int node_idx, int node_left, int node_right) {
            // kth >= 1
            if (node_right - node_left == 1) return node_idx - node_size_ + 1;
            if (node_[node_idx * 2 + 1] < kth) return _search(kth - node_[node_idx * 2 + 1], node_idx * 2 + 2, (node_left + node_right) / 2, node_right);
            else return _search(kth, node_idx * 2 + 1, node_left, (node_left + node_right) / 2);
        }
        int search(int kth) {
            return _search(kth, 0, 0, node_size_);
        }
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N, Q;
    string S;
    cin >> N >> S >> Q;
    vector<SegTree<int>> segs(26, SegTree<int>(N, 0, [](int a, int b) {return a + b;}, [](int a, int b) {return a + b;}));
    rep(i, 0, N) {
        segs[S[i] - 'a'].change(i, 1);
    }
    int q_type, l, r, idx;
    char c;
    rep(i, 0, Q) {
        cin >> q_type;
        if (q_type == 1) {
            cin >> idx >> c;
            --idx;
            segs[S[idx] - 'a'].change(idx, -1);
            segs[c - 'a'].change(idx, 1);
            S[idx] = c;
        }
        else {
            cin >> l >> r;
            --l;
            int res = 0;
            rep(j, 0, 26) {
                if (segs[j].query(l, r) > 0) {
                    ++res;
                }
            }
            cout << res << endl;
        }
    }
    return 0;
}

Measured memory_bytes: 111516