#include <bits/stdc++.h>
#include <unistd.h>
#include <sys/time.h>
#include <stdlib.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<P, ll> T;
typedef pair<long double , ll> Ps;
typedef pair<ll, bool> Pb;

const ll INF = 1e18;
const ll fact_table = 3200008;
long double Pi = 3.1415926535897932384626;

priority_queue <ll> pql;
priority_queue <P> pqp;
priority_queue <P> bag;
//big priority queue
priority_queue <ll, vector<ll>, greater<ll> > pqls;
priority_queue <P, vector<P>, greater<P> > pqps;
//small priority queue
//top pop

ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
ll dy[8] = {0, 1, 0, -1, 1, -1, -1, 1};
//↓,→,↑,←


#define endl "\n"
#ifdef ENJAPMA
#undef endl
#endif

#define p(x) cout<<x<<endl;
#define el cout<<endl;
#define pe(x) cout<<x<<" ";
#define ps(x) cout<<fixed<<setprecision(25)<<x<<endl;
#define pu(x) cout<<(x);
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define CLEAR(a) a = decltype(a)();
#define pc(x) cout << x << ",";
#define rep(i, n) for (ll i = 0; i < (n); i ++)

// const ll mod = 998244353ll;
const ll mod = 1000000007ll;

ll mypow(ll a, ll b, ll mod) {ll x = 1; while (b) {while (!(b & 1)) {(a *= a) %= mod; b >>= 1;}(x *= a) %= mod; b--;} return x;}
void YES(bool cond) { if (cond) { p("YES");} else { p("NO");} return;}
void Yes(bool cond) { if (cond) { p("Yes");} else { p("No");} return;}
void line() { p("--------------------"); return;}

/*
ll fact[fact_table + 5], rfact[fact_table + 5];

void c3_init() {
    fact[0] = rfact[0] = 1;
    for (ll i = 1; i <= fact_table; i++) {
        fact[i] = (fact[i - 1] * i) % mod;
    }
    rfact[fact_table] = mypow(fact[fact_table], mod - 2, mod);
    for (ll i = fact_table; i >= 1; i--) {
        rfact[i - 1] = rfact[i] * i;
        rfact[i - 1] %= mod;
    }
    return;
}
ll c3(ll n, ll r) {
    return (((fact[n] * rfact[r]) % mod ) * rfact[n - r]) % mod;
}
*/
struct Timer {
    int64_t start;
    const int64_t CYCLES_PER_SEC = 2800000000;
    Timer() { reset(); }
    void reset() { start = getCycle(); }
    inline double get() { return (double)(getCycle() - start) / CYCLES_PER_SEC; }
    inline int64_t getCycle() {
        uint32_t low, high;
        __asm__ volatile ("rdtsc" : "=a" (low), "=d" (high));
        return ((int64_t)low) | ((int64_t)high << 32);
    }
};

bool multicase = false;

ll n, m, k, w, a, b, c, d, e, h, q, sum, l;

typedef vector<ll> vec;
typedef vector<vector<ll>> mat;

struct BIT {
private:
    int n;
    vector<ll> bit[2];
public:
    void init(vector<ll> v) {
        // vectorでBITを初期化する
        // BIT seg(vector<ll>(n, 0ll));
        n = v.size() + 1;
        bit[0].resize(n);
        bit[1].resize(n);
        bit[0][0] = 0;
        for (int i = 0; i < n - 1; i++) {
            bit[0][i + 1] = bit[0][i] + v[i];
            bit[1][i] = 0;
        }
    }
    void add_sub(int p, int i, ll x) {
        for (int idx = i; idx < n; idx += (idx & -idx)) {
            bit[p][idx] += x;
        }
    }
    // [a, b)にxを加算する
    void add(int a, int b, ll x) {
        add_sub(0, a, -x * (a - 1));
        add_sub(0, b, x * (b - 1));
        add_sub(1, a, x);
        add_sub(1, b, -x);
    }
    ll sum_sub(int p, int i) {
        ll sum = 0;
        for (int idx = i; idx > 0; idx -= (idx & -idx)) {
            sum += bit[p][idx];
        }
        return sum;
    }
    // [a, b)の範囲の区間和を取得する
    ll getsum(int a, int b) {
        ll sum1 = sum_sub(0, b - 1) + sum_sub(1, b - 1) * (b - 1);
        ll sum2 = sum_sub(0, a - 1) + sum_sub(1, a - 1) * (a - 1);
        return sum1 - sum2;
    }
};

BIT seg[26];

void solve() {
    cin >> n;
    for (int i = 0; i < 26; i++) {
        seg[i].init((vec(n + 10, 0)));
    }
    string s;
    cin >> s;
    cin >> q;
    for (int i = 0; i < n; i++) {
        int c = s[i] - 'a';
        seg[c].add(i + 1, i + 2, 1);
    }
    for (int i = 0; i < q; i++) {
        int type;
        cin >> type;
        if (type == 1) {
            int idx;
            char c;
            cin >> idx >> c;
            int id = s[idx - 1] - 'a';
            seg[id].add(idx, idx + 1, -1);
            id = c - 'a';
            seg[id].add(idx, idx + 1, 1);
            s[idx - 1] = (char)c;
        } else {
            ll res = 0;
            int l, r;
            cin >> l >> r;
            for (int j = 0; j < 26; j++) {
                if (seg[j].getsum(l, r + 1) >= 1) {
                    res ++;
                }
            }
            p(res);
        }
    }
    return;
}

int main() {
    // init();
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll q, testcase = 1;
    if (multicase) {
        cin >> q;
    } else {
        q = 1;
    }
    while (q--) {
        // pu("Case ");pu("#");pu(testcase);pu(": ");
        solve();
        testcase++;
    }
    // solve();
    return 0;
}



Measured memory_bytes: 210244