#include <bits/stdc++.h>
using namespace std;

// Define
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template <class T> using pvector = vector<pair<T, T>>;
template <class T>
using rpriority_queue = priority_queue<T, vector<T>, greater<T>>;
constexpr const ll dx[4] = {1, 0, -1, 0};
constexpr const ll dy[4] = {0, 1, 0, -1};
constexpr const ll MOD = 1e9 + 7;
constexpr const ll mod = 998244353;
constexpr const ll INF = 1LL << 60;
constexpr const ll inf = 1 << 30;
constexpr const char rt = '\n';
constexpr const char sp = ' ';
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define eb emplace_back
#define elif else if
#define all(a, v, ...)                                                         \
    ([&](decltype((v)) w) { return (a)(begin(w), end(w), ##__VA_ARGS__); })(v)
#define fi first
#define se second

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;
}

// Debug
#define debug(...)                                                             \
    {                                                                          \
        cerr << __LINE__ << ": " << #__VA_ARGS__ << " = ";                     \
        for (auto &&X : {__VA_ARGS__}) cerr << "[" << X << "] ";               \
        cerr << rt;                                                            \
    }

#define dump(a, h, w)                                                          \
    {                                                                          \
        cerr << __LINE__ << ": " << #a << " = [" << rt;                        \
        rep(i, h) {                                                            \
            rep(j, w) cerr << a[i][j] << sp;                                   \
            cerr << rt;                                                        \
        }                                                                      \
        cerr << "]" << rt;                                                     \
    }

#define vdump(a, n)                                                            \
    {                                                                          \
        cerr << __LINE__ << ": " << #a << " = [";                              \
        rep(i, n) if (i) cerr << sp << a[i];                                   \
        else cerr << a[i];                                                     \
        cerr << "]" << rt;                                                     \
    }

// Loop
#define inc(i, a, n) for (ll i = (a), _##i = (n); i <= _##i; ++i)
#define dec(i, a, n) for (ll i = (a), _##i = (n); i >= _##i; --i)
#define rep(i, n) for (ll i = 0, _##i = (n); i < _##i; ++i)
#define each(i, a) for (auto &&i : a)

// Stream
#define fout(n) cout << fixed << setprecision(n)
struct io {
    io() { cin.tie(nullptr), ios::sync_with_stdio(false); }
} io;

// Speed
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

// Math
inline constexpr ll gcd(const ll a, const ll b) {
    return b ? gcd(b, a % b) : a;
}
inline constexpr ll lcm(const ll a, const ll b) { return a / gcd(a, b) * b; }

inline constexpr ll modulo(const ll n, const ll m = MOD) {
    ll k = n % m;
    return k + m * (k < 0);
}
inline constexpr ll chmod(ll &n, const ll m = MOD) {
    n %= m;
    return n += m * (n < 0);
}
inline constexpr ll mpow(ll a, ll n, const ll m = MOD) {
    ll r = 1;
    rep(i, 64) {
        if (n & (1LL << i)) r *= a;
        chmod(r, m);
        a *= a;
        chmod(a, m);
    }
    return r;
}
inline ll inv(const ll n, const ll m = MOD) {
    ll a = n, b = m, x = 1, y = 0;
    while (b) {
        ll t = a / b;
        a -= t * b;
        swap(a, b);
        x -= t * y;
        swap(x, y);
    }
    return modulo(x, m);
}

struct RASQ {
    static const ll n = 1LL << 20;
    vector<ll> node, lazy;
    RASQ() : node(n * 2 - 1), lazy(n * 2 - 1) {}
    inline void eval(ll i, ll l, ll r) {
        node[i] += lazy[i];
        if (r - l > 1) {
            lazy[i * 2 + 1] += lazy[i] / 2;
            lazy[i * 2 + 2] += lazy[i] / 2;
        }
        lazy[i] = 0;
    }
    inline void add(ll a, ll b, ll x, ll i = 0, ll l = 0, ll r = 1LL << 20) {
        eval(i, l, r);
        if (b <= l || r <= a) return;
        if (a <= l && r <= b) {
            lazy[i] += (r - l) * x;
            eval(i, l, r);
        } else {
            add(a, b, x, i * 2 + 1, l, (l + r) / 2);
            add(a, b, x, i * 2 + 2, (l + r) / 2, r);
            node[i] = node[i * 2 + 1] + node[i * 2 + 2];
        }
    }
    inline ll sum(ll a, ll b, ll i = 0, ll l = 0, ll r = 1LL << 20) {
        if (b <= l || r <= a) return 0;
        eval(i, l, r);
        if (a <= l && r <= b) return node[i];
        return sum(a, b, i * 2 + 1, l, (l + r) / 2) +
               sum(a, b, i * 2 + 2, (l + r) / 2, r);
    }
};

signed main() {
    ll N, Q;
    string S;
    cin >> N >> S >> Q;
    RASQ segtree[26];
    rep(i, N) segtree[S[i] - 'a'].add(i, i + 1, 1);
    rep(i, Q) {
        ll A;
        cin >> A;
        if (A == 1) {
            ll B;
            char C;
            cin >> B >> C;
            segtree[S[B - 1] - 'a'].add(B - 1, B, -1);
            S[B - 1] = char(C);
            segtree[S[B - 1] - 'a'].add(B - 1, B, 1);
        } else {
            ll B, C;
            cin >> B >> C;
            ll res = 0;
            rep(i, 26) res += !!segtree[i].sum(B - 1, C);
            cout << res << endl;
        }
    }
}

// -g -D_GLIBCXX_DEBUG -fsanitize=undefined


Measured memory_bytes: 853148