import std.stdio, std.string, std.conv, std.range;
import std.algorithm, std.array, std.typecons, std.container;
import std.math, std.numeric, std.random, core.bitop;

enum inf = 1_001_001_001;
enum infl = 1_001_001_001_001_001_001L;

void main() {
    int N;
    scan(N);
    auto s = readln.chomp.map!(ch => ch - 'a').array;

    auto rbt = new RedBlackTree!int[](26);
    foreach (i ; 0 .. 26) {
        rbt[i] = redBlackTree!(int)();
    }
    foreach (i ; 0 .. N) {
        rbt[s[i]].insert(i);
    }

    int Q;
    scan(Q);
    foreach (_ ; 0 .. Q) {
        auto ln = readln.split;
        if (ln.front == "1") {
            int idx = ln[1].to!int - 1;
            int c = ln[2].to!char - 'a';
            rbt[s[idx]].removeKey(idx);
            rbt[c].insert(idx);
            s[idx] = c;
        }
        else {
            int l = ln[1].to!int - 1;
            int r = ln[2].to!int;
            int ans;
            foreach (i ; 0 .. 26) {
                auto up = rbt[i].upperBound(l - 1);
                if (!up.empty && up.front < r) {
                    ans++;
                }
            }
            writeln(ans);
        }
    }
    
}



void scan(T...)(ref T args) {
    auto line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront;
    }
    assert(line.empty);
}

void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}

bool chmin(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x > arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

bool chmax(T, U...)(ref T x, U args) {
    bool isChanged;
    foreach (arg; args) if (x < arg) {
        x = arg;
        isChanged = true;
    }
    return isChanged;
}

void yes(bool ok, string y = "Yes", string n = "No") {
    return writeln(ok ? y : n);
}