#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define countof(array) (sizeof(array) / sizeof(array[0]))
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = (n)-1; i >= 0; --i)
#define rep2(i,n) for(int i = 1; i <= (n); ++i)
#define rrep2(i,n) for(int i = (n); i > 0; --i)
#define srep(i,s,n) for(int i = s; i < (n); ++i)
#define rsrep(i,s,n) for(int i = (n)-1; i >= s; --i)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define aall(a) (a), (a)+countof(a)//for array sorting
#define raall(a) (a), (a)+countof(a), greater<>()
#define show(x) cout<<#x<<" = "<<(x)<<endl;
#define vfind(v, a) find(all(v), a) != v.end()
#define yn(f) { if (f) puts("YES"); else puts("NO"); }
#define yns(f) { if (f) puts("Yes"); else puts("No"); }
#define show_ary(...) { cout<<#__VA_ARGS__<<" = "; for (const auto& x : (__VA_ARGS__)) { cout<<x<<" "; } cout<<endl; }
#define show_pair(...) cout<<#__VA_ARGS__<<" = "<<endl; for (const auto& x : (__VA_ARGS__)) { cout<<"  "<<x.fi<<" : "<<x.se<<endl; }
#define out_ary(...) { int n = (__VA_ARGS__).size(); rep(i, n) printf("%d%s", (__VA_ARGS__)[i], i != n-1 ? " " : "\n"); }
#define argmax(v) distance((v).begin(), max_element(all(v)))
#define argmin(v) distance((v).begin(), min_element(all(v)))
#define vmax(v) *max_element(all(v))
#define vmin(v) *min_element(all(v))
typedef long long int ll;
typedef pair<int, int> P;
typedef vector<P> vpair;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef vector<double> vdouble;
typedef vector<string> vstr;
typedef vector<bool> vbool;
typedef vector<vint> vvint;
typedef vector<vll> vvll;
typedef vector<vstr> vvstr;
typedef vector<vbool> vvbool;
const ll LINF = 2000000000000000000ll;
const int INF = 1000000100;
const ll MOD = 1e9+7;

struct SegmentTree {
    int n;
    vector<int> node;
    SegmentTree(int sz) {
        n = 1; while(n < sz) n *= 2;
        node.resize(2*n-1, 0);
        // for(int i=0; i<sz; i++) node[i+n-1] = 0;
        for(int i=n-2; i>=0; i--) node[i] = max(node[2*i+1], node[2*i+2]);
    }

    void update(int k, int val) {
        k += (n - 1);
        node[k] = val;
        while(k > 0) {
            k = (k - 1) / 2;
            node[k] = max(node[2*k+1], node[2*k+2]);
        }
    }

    int query(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 vl = query(a, b, 2*k+1, l, (l+r)/2);
        int vr = query(a, b, 2*k+2, (l+r)/2, r);
        return max(vl, vr);
    }
};

int main() {
    int n;
    string s;
    int q;
    cin >> n >> s >> q;
    int sl = s.length();
    vector<SegmentTree> st(26, SegmentTree(sl));

    rep(i, sl) {
        st[s[i]-97].update(i, 1);
    }

    rep(i, q) {
        int a, b, c;
        char d;
        cin >> a;
        if (a == 1) {
            cin >> b >> d;
            --b;
            st[s[b]-97].update(b, 0);
            st[d-97].update(b, 1);
            s[b] = d;
        }
        else {
            cin >> b >> c;
            --b;
            --c;
            int ans = 0;
            rep(j, 26) {
                if (st[j].query(b, c+1)) ans++;
            }
            cout << ans << endl;
        }
    }

    return 0;
}

Measured memory_bytes: 111620