#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define pli pair<ll, int>
#define pil pair<int, ll>
#define pll pair<ll, ll>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
#define endl '\n'
const int inf = 1000000007;
const ll INF = 1e18;
// int mod = 998244353;
int mod = 1000000007;
const double eps = 1e-8;
#define abs(x) (x >= 0 ? x : -(x))
#define lb(v, x) (int)(lower_bound(all(v), x) - v.begin())
#define ub(v, x) (int)(upper_bound(all(v), x) - v.begin())
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { if (a < b) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { if (b == 0) return a; return gcd(b, a % b); }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template<typename T, typename U> T pow_(T a, U b) { return b ? pow_(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
ll modpow(ll a, ll b, ll _mod) { return b ? modpow(a * a % _mod, b / 2, _mod) * (b % 2 ? a : 1) % _mod : 1; }
template<class T, class U> ostream& operator << (ostream& os, const pair<T, U>& p) { os << p.F << " " << p.S; return os; }
template<class T> ostream& operator << (ostream& os, const vector<T>& vec) { rep(i, sz(vec)) { if (i) os << " "; os << vec[i]; } return os; }
template<class T> ostream& operator << (ostream& os, const set<T>& s) { for (auto si : s) os << si << " "; return os; }
template<typename T> inline istream& operator >> (istream& is, vector<T>& v) { rep(j, sz(v)) is >> v[j]; return is; }
template<class T, class T2> inline void add(T &a, T2 b) { (a += (b % mod + mod)) %= mod; }
template<class T> void operator += (vector<T>& v, vector<T> v2) { rep(i, sz(v2)) v.eb(v2[i]); }

void solve();

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(12);
    int T;
    T = 1;
    while (T--) solve();
}

struct UnionFind {
    vector<double> data;
    int sz;
    UnionFind(int _sz) : data(_sz, -1) { sz = _sz; }
    bool connect(int x, int y) {
        if ((x = root(x)) == (y = root(y))) return false;
        if (data[x] > data[y]) swap(x, y);
        data[x] += data[y]; data[y] = x; sz--;
        return true;
    }
    bool issame(int x, int y) { return root(x) == root(y); }
    int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
    int size(int x) { return -data[root(x)]; }
    int size() { return sz; }
};

template<typename T>
struct BIT {
    vector<vector<T> > array;
    int n, m;
    BIT(int _n, int _m)
    : array(_n, vector<T>(_m)), n(_n), m(_m) {}
public:
    // [0, x), [0, y)
    T sum(int x, int y) {
        T s = 0;
        for (int i = x - 1; i >= 0; i = (i & (i + 1)) - 1) {
            for (int j = y - 1; j >= 0; j = (j & (j + 1)) - 1) {
                s += array[i][j];
            }
        }
        return s;
    }
    // [x1, x2), [y1, y2)
    T sum(int x1, int x2, int y1, int y2) {
        return sum(x2, y2) - sum(x1, y2) - sum(x2, y1) + sum(x1, y1);
    }
    void add(int x, int y, T k) {
        for (int i = x; i < n; i |= i + 1) {
            for (int j = y; j < m; j |= j + 1) {
                array[i][j] += k;
            }
        }
    }
};
// BITでmodとってたら遅い

void solve() {
    int n;
    cin >> n;
    string s;
    cin >> s;
    
    BIT<int> bit(26, n);
    rep(i, n) {
        int x = s[i] - 'a';
        bit.add(x, i, 1);
    }
    
    int q;
    cin >> q;
    while (q--) {
        int k;
        cin >> k;
        if (k == 1) {
            int a; char c;
            cin >> a >> c;
            --a;
            bit.add(s[a] - 'a', a, -1);
            bit.add(c - 'a', a, 1);
            s[a] = c;
        } else {
            int l, r;
            cin >> l >> r;
            --l; --r;
            
            int ans = 0;
            rep(i, 26) if (bit.sum(i, i + 1, l, r + 1)) ++ans;
            cout << ans << endl;
        }
    }
}


Measured memory_bytes: 56536