#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define pp pair<pair<ll, ll>,pair<ll, ll>>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define vii vector<int>
#define vll vector<ll>
#define mat vector<vector<ll>>
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define fi first
#define sc second
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep2(i,a,b) for(ll i=a;i<b;i++)
#define repr(i,n) for(ll i=n-1;i>=0;i--)
#define all(x) x.begin(),x.end()
#define sz(x) (ll) (x).size()
#define pq priority_queue<ll>
#define pqg priority_queue<ll,vector<ll>,greater<ll>>
#define LB(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define UB(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
#define ERASE(v) sort(v.begin(),v.end());v.erase(unique(v.begin(),v.end()),v.end())
#define int ll
using namespace std;
const ll INF = (1 << 30 ) - 1;
const ll LLINF = (1LL << 60LL);
const ll MOD = 1000000007;
const ll mod = 998244353;
const ll MAX = 1100000;
const double pi = acos(-1);
const double eps = 1e-10;
ll dx[4] ={1,0,-1,0} , dy[4] ={0,1,0,-1};

template<class T> 
inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> 
inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

struct Timer{
    chrono::system_clock::time_point start, end;
    Timer(){ start = chrono::system_clock::now(); }
    ~Timer(){
        end = chrono::system_clock::now();
        auto msec = chrono::duration_cast<chrono::milliseconds>(end - start).count();
        cerr<<"time : "<<msec<<" ms"<<endl;
    }
};



struct SegmentTree{
    static const int MAX_N = 1<<19;
    int n,dat[2 * MAX_N -1];
    SegmentTree(int n_){
        n=1;
        while(n<n_) n*= 2;
        for(int i=0;i<2*n-1;i++) dat[i] = 0;
    }
    void update(int k,int a){
        k += n-1;
        dat[k]=(1<<a);
        while(k>0){
            k=(k-1)/2;
            // dat[k]=min(dat[k*2+1],dat[k*2+2]);
            dat[k]=(dat[k*2+1]|dat[k*2+2]);
        }
    }
    void print(){
        rep(i,n*2){
            // if(i==n-1) cout<<"//";
            // cout<<dat[i]<<" ";
        }
        // cout<<endl;
    }
    int query(int a,int b,int k,int l,int r){
        if(r<=a || b<=l) return 0;
        if(a<=l && r<=b){
            return dat[k];
        }
        else{
            int vl = query(a,b,k*2+1,l,(l+r)/2);
            int vr= query(a,b,k*2+2,(l+r)/2,r);
            return (vr|vl);
        }
    }
    int query(int a,int b){
        return query(a,b,0,0,n);
    }
};

void solve(){
    ll n,q;
    cin>>n;
    string s;
    cin>>s>>q;
    SegmentTree sg(n);
    rep(i,n){
        sg.update(i,s[i]-'a');
    }
    // sg.print();
    // cout<<"------"<<endl;
    rep(i,q){
        // sg.print();
        ll c;
        cin>>c;
        if(c==1){
            ll a;
            char b;
            cin>>a>>b;
            sg.update(a-1,b-'a');
        }
        else{
            ll a,b;
            cin>>a>>b;
            ll t=sg.query(a-1,b);
            ll sum=0;
            rep(j,26){
                if(t&(1<<j)) sum++;
            }
            cout<<sum<<endl;
        }
    }
}


signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    // Timer TM;
    
    solve();

    return 0;
}


Measured memory_bytes: 9116