Language: C++

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, a, b) for(int i = a; i < b; i++)
#define rrep(i, a, b) for(int i = b - 1; i >= a; i--)
#define ALL(a) a.begin(), a.end()
#define pii pair<int,int>
#pragma GCC optimize("Ofast")
#define pcnt __builtin_popcount
#define buli(x) __builtin_popcountll(x)
#define pb push_back
#define mp make_pair
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define isSquare(x) (sqrt(x)*sqrt(x) == x)
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(a>b){a = b; return 1;} return 0; };
inline void IN(void){return;}
template <typename First, typename... Rest> void IN(First& first, Rest&... rest){cin >> first;IN(rest...);return;}
inline void OUT(void){cout << "\n";return;}
template <typename First, typename... Rest> void OUT(First first, Rest... rest){cout << first << " ";OUT(rest...);return;}
const double EPS = 1e-9;
const int mod = 1e9 + 7;
const int INF = 1e9;
const long long LLINF = 1e18;
long long lcm(ll a, ll b){return a * b / __gcd(a,b);}
struct IoSetup { IoSetup() {
    cin.tie(nullptr);ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
} } iosetup;
template< int mod > struct ModInt {
    int x; ModInt() : x(0) {}
    ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
    ModInt &operator+=(const ModInt &p) {if((x += p.x) >= mod) x -= mod;return *this;}
    ModInt &operator-=(const ModInt &p) {if((x += mod - p.x) >= mod) x -= mod;return *this;}
    ModInt &operator*=(const ModInt &p) {x = (int) (1LL * x * p.x % mod);return *this;}
    ModInt &operator/=(const ModInt &p) {*this *= p.inverse();return *this;}
    ModInt operator-() const { return ModInt(-x); }
    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
    bool operator==(const ModInt &p) const { return x == p.x; }
    bool operator!=(const ModInt &p) const { return x != p.x; }
    ModInt inverse() const {int a = x, b = mod, u = 1, v = 0, t;
    while(b > 0) { t = a / b; swap(a -= t * b, b); swap(u -= t * v, v); }return ModInt(u);}
    ModInt pow(int64_t n) const {ModInt ret(1), mul(x); while(n > 0) {if(n & 1) ret *= mul;mul *= mul;n >>= 1;}return ret;}
    friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x;}
    friend istream &operator>>(istream &is, ModInt &a) { int64_t t; is >> t; a = ModInt< mod >(t); return (is); }
    static int get_mod() { return mod; }
}; using modint = ModInt< mod >;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

int main(){
    iosetup;

    return 0;
}


struct SegmentTree{
    private:
        int n;
        vector<int> node;
    
    public:
        SegmentTree(string v){
            int sz = v.size();
            n = 1; while(n < sz) n *= 2;
            node.resize(2 * n - 1);
            for(int i = 0; i < sz; i++) node[i+n-1] |= 1 << (v[i] - 'a');
            for(int i = n - 2; i >= 0; i--){
                node[i] = ( node[2*i+1] | node[2*i+2]);
            }
        }

        void update(int x, char val){
            x += n - 1;
            if(node[x] == (1 << (val - 'a'))) return;
            node[x] = (1 << (val - 'a'));
            while(x > 0){
                x = (x - 1) / 2;
                node[x] = ( node[2*x+1] | node[2*x+2]);
            }
        }

        int get(int a, int b, int k = 0, int l = 0, int r = -1){
            if(r < 0) r = n;
            if(r <= a || b <= l) return 0;
            if(a <= l && r <= b) return node[k];
            int res = 0;

            auto vl = get(a, b, 2*k+1, l, (l+r)/2);
            auto vr = get(a, b, 2*k+2, (l+r)/2, r);
            res = (vl | vr);
            return res;
        }
};

int main(){
    int N; cin >> N;
    string S; cin >> S;
    int Q; cin >> Q;
    SegmentTree seg(S);
    while(Q--){
        int q; cin >> q;
        if(q == 1){
            int i; char c; cin >> i >> c; i--;
            seg.update(i, c);
        }else{
            int l, r; cin >> l >> r; l--, r--;
            auto M = seg.get(l, r + 1);
            cout << pcnt(M) << endl;
        }
    }
    return 0;
}


Compiler output:
a.cc:101:5: error: redefinition of 'int main()'
  101 | int main(){
      |     ^~~~
a.cc:55:5: note: 'int main()' previously defined here
   55 | int main(){
      |     ^~~~