#include<bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
typedef long long ll;
#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define REP(i,num,n) for(int i=num, i##_len=(n); i<i##_len; ++i)
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
#define print(x) (cout << (x) << endl)
#define pb push_back
#define mp make_pair
#define sz(x) int(x.size())
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class itr> void array_output(itr start, itr goal){ string ans; for(auto i = start; i != goal; i++) ans += to_string(*i) + " "; if(!ans.empty()) ans.pop_back(); cout << ans << endl; }
#define fs first
#define sc second

const int INF = 1e9;
const ll LLINF = 1e16;
const ll MOD = 1e9+7;
template<class T> inline void add(T &a, T b){a = ((a+b) % MOD + MOD) % MOD;};

template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}
 
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}
 

// 指定した文字cが文字列に何文字入ってるか
ll stringcount(string s, char c) {
    return count(s.cbegin(), s.cend(), c);
}


// 割り算の切り上げ処理
template<typename T>
T rp(T a, T b) {
  return (a + b - 1) / b;
}

// 桁和
template<typename T>
T digsum(T n) {
    T res = 0;
    while(n > 0) {
        res += n%10;
        n /= 10;
    }
    return res;
}

// 回文判定
bool kai (string s) {
    string t{s};
    reverse(begin(t), end(t));
    return s == t;
}

using pint = pair<int, int>;
using pll = pair<ll, ll>;




template<class Monoid> struct SegTree {
    using Func = function<Monoid(Monoid, Monoid)>;
    const Func F;
    const Monoid UNITY;
    int SIZE_R;
    vector<Monoid> dat;
    
    SegTree(int n, const Func f, const Monoid &unity): F(f), UNITY(unity) { init(n); }
    void init(int n) {
        SIZE_R = 1;
        while (SIZE_R < n) SIZE_R *= 2;
        dat.assign(SIZE_R * 2, UNITY);
    }
    
    /* set, a is 0-indexed */
    void set(int a, const Monoid &v) { dat[a + SIZE_R] = v; }
    void build() {
        for (int k = SIZE_R - 1; k > 0; --k)
            dat[k] = F(dat[k*2], dat[k*2+1]);
    }
    
    /* update a, a is 0-indexed */
    void update(int a, const Monoid &v) {
        int k = a + SIZE_R;
        dat[k] = v;
        while (k >>= 1) dat[k] = F(dat[k*2], dat[k*2+1]);
    }
    
    /* get [a, b), a and b are 0-indexed */
    Monoid get(int a, int b) {
        Monoid vleft = UNITY, vright = UNITY;
        for (int left = a + SIZE_R, right = b + SIZE_R; left < right; left >>= 1, right >>= 1) {
            if (left & 1) vleft = F(vleft, dat[left++]);
            if (right & 1) vright = F(dat[--right], vright);
        }                                                                                                              
        return F(vleft, vright);
    }
    inline Monoid operator [] (int a) { return dat[a + SIZE_R]; }
    
    /* debug */
    void print_debug() {
        for (int i = 0; i < SIZE_R; ++i) {
            cout << (*this)[i];
            if (i != SIZE_R-1) cout << ",";
        }
        cout << endl;
    }
};

int main(void)
{
    cout.tie(0);
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
    int n,q;
    string s;
    cin >> n >> s >> q;
    vector<SegTree<int> > is(26, SegTree<int>(n + 10, [](int a, int b){ return a + b; }, 0));
    rep(i, n) is[s[i] - 'a'].update(i, 1); // 1-index
    rep(qi, q){
        int ty;
        cin >> ty;
        if (ty == 1){
            int i; char c;
            cin >> i >> c;
            --i;
            is[s[i] - 'a'].update(i, 0);
            s[i] = c;
            is[s[i] - 'a'].update(i, 1);
        } else {
            int l, r;
            cin >> l >> r;
            --l;
            int ans = 0;
            rep(i, 26){
                // 0-indexなので半開区間であるがrに+1する必要はない
                if(is[i].get(l, r)) ++ans;
            }
            print(ans);
        }
    } 


}


Measured memory_bytes: 111516