#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os, const map<T,U>& mp){ os << "{"; for(auto& p : mp){ os << p << ","; } os << "}"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
using ll = long long;
using ull = unsigned long long;
using pii = std::pair<int,int>;
using vi = std::vector<int>;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/

template<typename T,T iniv=0>
struct Segtree{
    int n;
    vector<T> dat;
    Segtree(int n_){
        n = 1;
        while(n < n_) n *= 2;
        dat.resize(2*n-1);
        for(int i=0;i<2*n-1;i++) dat[i]=iniv;
    }

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

    T query(int a,int b,int k,int l,int r){
        if(r<=a or b<=l) return iniv;
        else if(a<=l and r<=b) return dat[k];
        else{
            T vl = query(a,b,k*2+1,l,(l+r)/2);
            T vr = query(a,b,k*2+2,(l+r)/2,r);
            return max(vl,vr);
        }
    }

    T query(int a,int b){
        return query(a,b,0,0,n);
    }
};

int main(){
    int n; cin >> n;
    string s; cin >> s;

    using S = Segtree<long long,0>;
    vector<S> seg(26, S(n));
    for(int i=0;i<n;i++){
        int idx = s[i] - 'a';
        seg[idx].update(i, 1);
    }

    int q; cin >> q;
    rep(_,q){
        int t; cin >> t;
        if(t==1){
            int i;
            char c;
            cin >> i >> c;
            i--;
            int before = s[i]-'a';
            int after = c-'a';
            s[i] = c;
            seg[before].update(i, 0);
            seg[after].update(i, 1);
        }else{
            int l,r; cin >> l >> r;
            l--;
            int cnt = 0;
            for(int i=0;i<26;i++){
                cnt += seg[i].query(l,r);
            }
            cout << cnt << endl;
        }
    }
}


Measured memory_bytes: 222212