#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template<class T> inline void YES(T condition){ if(condition) cout << "YES" << endl; else cout << "NO" << endl; }
template<class T> inline void Yes(T condition){ if(condition) cout << "Yes" << endl; else cout << "No" << endl; }
template<class T = string, class U = char>int character_count(T text, U character){ int ans = 0; for(U i: text){ ans += (i == character); } return ans; }
lint power(lint base, lint exponent, lint module){ if(exponent % 2){ return power(base, exponent - 1, module) * base % module; }else if(exponent){ lint root_ans = power(base, exponent / 2, module); return root_ans * root_ans % module; }else{ return 1; }}
struct position{ int y, x; }; position mv[4] = {{0, -1}, {1, 0}, {0, 1}, {-1, 0}}; // double euclidean(position first, position second){ return sqrt((second.x - first.x) * (second.x - first.x) + (second.y - first.y) * (second.y - first.y)); }
template<class T, class U> string to_string(pair<T, U> x){ return to_string(x.first) + "," + to_string(x.second); } string to_string(string x){ return x; }
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; }
template<class itr> void cins(itr first, itr last){ for(auto i = first; i != last; i++){ cin >> (*i); } }
template<class T> T gcd(T a, T b){ if(a && b){ return gcd(min(a, b), max(a, b) % min(a, b)); }else{ return a; }} template<class T> T lcm(T a, T b){ return a / gcd(a, b) * b; }
struct combination{ vector<lint> fact, inv; combination(int sz) : fact(sz + 1), inv(sz + 1){ fact[0] = 1; for(int i = 1; i <= sz; i++){ fact[i] = fact[i - 1] * i % mod; } inv[sz] = power(fact[sz], mod - 2, mod); for(int i = sz - 1; i >= 0; i--){ inv[i] = inv[i + 1] * (i + 1) % mod; } } lint C(int p, int q) const{ if(q < 0 || p < q) return 0; return (fact[p] * inv[q] % mod * inv[p - q] % mod); } };
template<class itr> bool next_sequence(itr first, itr last, int max_bound){ itr now = last; while(now != first){ now--; (*now)++; if((*now) == max_bound){ (*now) = 0; }else{ return true; } } return false; }

template< typename Monoid >
struct SegmentTree
{
    using F = function< Monoid(Monoid, Monoid) >;
    
    int sz;
    vector< Monoid > seg;
    
    const F f;
    const Monoid M1;
    
    SegmentTree(int n, const F f, const Monoid &M1) : f(f), M1(M1)
    {
        sz = 1;
        while(sz < n) sz <<= 1;
        seg.assign(2 * sz, M1);
    }
    
    void set(int k, const Monoid &x)
    {
        seg[k + sz] = x;
    }
    
    void build()
    {
        for(int k = sz - 1; k > 0; k--) {
            seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
        }
    }
    
    void update(int k, const Monoid &x)
    {
        k += sz;
        seg[k] = x;
        while(k >>= 1) {
            seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
        }
    }
    
    Monoid query(int a, int b)
    {
        Monoid L = M1, R = M1;
        for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
            if(a & 1) L = f(L, seg[a++]);
            if(b & 1) R = f(seg[--b], R);
        }
        return f(L, R);
    }
    
    Monoid operator[](const int &k) const
    {
        return seg[k + sz];
    }
};

vector<SegmentTree<int>> seg;

int main(){
    int N, Q;
    string S;
    cin >> N >> S >> Q;
    seg = vector<SegmentTree<int>>(26, SegmentTree<int>(N, [](int a, int b){ return a + b; }, 0));
    for(int i = 0; i < N; i++){
        seg[S[i] - 'a'].set(i, 1);
    }
    for(int i = 0; i < 26; i++){
        seg[i].build();
    }
    for(int i = 0; i < Q; i++){
        int t;
        cin >> t;
        if(t == 1){
            int p;
            char q;
            cin >> p >> q;
            p--;
            seg[S[p] - 'a'].update(p, 0);
            seg[q - 'a'].update(p, 1);
            S[p] = q;
        }else{
            int l, r;
            cin >> l >> r;
            l--;
            int ans = 0;
            for(int j = 0; j < 26; j++){
                ans += !!seg[j].query(l, r);
            }
            cout << ans << endl;
        }
    }
}


Measured memory_bytes: 111620