#include <bits/stdc++.h>
using namespace std;
#define __ <<" "<<
#define ___ <<" "
#define bash push_back
#define ALL(x) x.begin(),x.end()
//#define int long long

struct IoSetup {
    IoSetup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(10);
        cerr << fixed << setprecision(10);
    }
}IoSetup;

typedef long long ll;
typedef pair < int , int >  pii;
static const signed int INF = 0x3f3f3f3f;
static const signed long long LINF = 0x3f3f3f3f3f3f3f3fLL;
static const signed int SMOD = 1000000007;
static const signed int NMOD = 998244353;
static const signed int dx[]={1,0,-1,0,1,1,-1,-1};
static const signed int dy[]={0,-1,0,1,-1,1,-1,1};

inline bool inside(int x,int y,int w,int h){return (x>=0 && y>=0 && x<w && y<h);}
template<class T>bool chmax(T &a, const T&b){if(a<b)return(a=b,1);return 0;}
template<class T>bool chmin(T &a, const T&b){if(b<a)return(a=b,1);return 0;}

#include <bits/stdc++.h>

template< typename Monoid, typename OperatorMonoid = Monoid >
struct LazySegmentTree {
    using F = function< Monoid(Monoid, Monoid) >;
    using G = function< Monoid(Monoid, OperatorMonoid) >;
    using H = function< OperatorMonoid(OperatorMonoid, OperatorMonoid) >;

    int sz, height;
    vector< Monoid > data;
    vector< OperatorMonoid > lazy;
    const F f;
    const G g;
    const H h;
    const Monoid M1;
    const OperatorMonoid OM0;


    LazySegmentTree(int n, const F f, const G g, const H h,
                    const Monoid &M1, const OperatorMonoid OM0)
        : f(f), g(g), h(h), M1(M1), OM0(OM0) {
        sz = 1;
        height = 0;
        while(sz < n) sz <<= 1, height++;
        data.assign(2 * sz, M1);
        lazy.assign(2 * sz, OM0);
    }

    void set(int k, const Monoid &x) {
        data[k + sz] = x;
    }

    void build() {
        for(int k = sz - 1; k > 0; k--) {
            data[k] = f(data[2 * k + 0], data[2 * k + 1]);
        }
    }

    inline void propagate(int k) {
        if(lazy[k] != OM0) {
            lazy[2 * k + 0] = h(lazy[2 * k + 0], lazy[k]);
            lazy[2 * k + 1] = h(lazy[2 * k + 1], lazy[k]);
            data[k] = reflect(k);
            lazy[k] = OM0;
        }
    }

    inline Monoid reflect(int k) {
        return lazy[k] == OM0 ? data[k] : g(data[k], lazy[k]);
    }

    inline void recalc(int k) {
        while(k >>= 1) data[k] = f(reflect(2 * k + 0), reflect(2 * k + 1));
    }

    inline void thrust(int k) {
        for(int i = height; i > 0; i--) propagate(k >> i);
    }

    void update(int a, int b, const OperatorMonoid &x) {
        thrust(a += sz);
        thrust(b += sz - 1);
        for(int l = a, r = b + 1; l < r; l >>= 1, r >>= 1) {
            if(l & 1) lazy[l] = h(lazy[l], x), ++l;
            if(r & 1) --r, lazy[r] = h(lazy[r], x);
        }
        recalc(a);
        recalc(b);
    }

    Monoid query(int a, int b) {
        thrust(a += sz);
        thrust(b += sz - 1);
        Monoid L = M1, R = M1;
        for(int l = a, r = b + 1; l < r; l >>= 1, r >>= 1) {
            if(l & 1) L = f(L, reflect(l++));
            if(r & 1) R = f(reflect(--r), R);
        }
        return f(L, R);
    }

    Monoid operator[](const int &k) {
        return query(k, k + 1);
    }

    template< typename C >
    int find_subtree(int a, const C &check, Monoid &M, bool type) {
        while(a < sz) {
        propagate(a);
        Monoid nxt = type ? f(reflect(2 * a + type), M) : f(M, reflect(2 * a + type));
        if(check(nxt)) a = 2 * a + type;
        else M = nxt, a = 2 * a + 1 - type;
        }
        return a - sz;
    }

    template< typename C >
    int find_first(int a, const C &check) {
        Monoid L = M1;
        if(a <= 0) {
        if(check(f(L, reflect(1)))) return find_subtree(1, check, L, false);
        return -1;
        }
        thrust(a + sz);
        int b = sz;
        for(a += sz, b += sz; a < b; a >>= 1, b >>= 1) {
        if(a & 1) {
            Monoid nxt = f(L, reflect(a));
            if(check(nxt)) return find_subtree(a, check, L, false);
            L = nxt;
            ++a;
        }
        }
        return -1;
    }


    template< typename C >
    int find_last(int b, const C &check) {
        Monoid R = M1;
        if(b >= sz) {
        if(check(f(reflect(1), R))) return find_subtree(1, check, R, true);
        return -1;
        }
        thrust(b + sz - 1);
        int a = sz;
        for(b += sz; a < b; a >>= 1, b >>= 1) {
        if(b & 1) {
            Monoid nxt = f(reflect(--b), R);
            if(check(nxt)) return find_subtree(b, check, R, true);
            R = nxt;
        }
        }
        return -1;
    }
};


signed main() {

    int n, q, x, y, z;
    string s;
    char c;

    cin >> n >> s >> q;

        
    using X = int;
    using M = int;
    LazySegmentTree<X, M> lseg(n,   [](X a, X b){return a | b;},
                                    [](X a, M b){return b;},
                                    [](M a, M b){return b;}, 0, 0);

    for(int i = 0; i < n; i++) {
        lseg.set(i, 1 << (s[i] - 'a'));
    }

    lseg.build();

    for(int i = 0; i < q; i++) {
        cin >> x;
        if(x == 1) {
            cin >> y >> c;
            lseg.update(y - 1, y, 1 << (c - 'a'));
        }
        else {
            cin >> y >> z;
            auto r = lseg.query(y-1, z);
            cout << __builtin_popcount(r) << endl;
        }
    }

    return 0;
}


Measured memory_bytes: 11872