#include <bits/stdc++.h>
using namespace std;

//定数
const long long MOD1=1000000007;
const long long MOD2=998244353;
const long double PI=3.1415926535897932;
const long long MAXLL=9223372036854775807;
const long long INF=2305843009213693951;
const long long dx[]={0,1,0,-1,1,-1,1,-1};
const long long dy[]={1,0,-1,0,1,1,-1,-1};

//省略
#define ll long long
#define ull unsigned long long
#define ld long double
#define uld unsigned long double
#define pll pair<long long,long long>
#define vl vector<long long>
#define vvl vector<vector<long long>>
#define vvvl vector<vector<vector<long long>>>
#define vc vector<char>
#define vvc vector<vector<char>>
#define vs vector<string>
#define vb vector<bool>
#define vvb vector<vector<bool>>
#define vp vector<pair<long long,long long>>
#define umap unordered_map
#define uset unordered_set
#define Lqueue priority_queue<long long>
#define Squeue priority_queue<long long,vector<long long>,greater<long long>>
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back

//マクロ
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define rbf(a,x) for(auto& a:x)
#define rep(i,n) for(long long i=0;i<(long long)(n);i++)
#define rep2(i,s,n) for(long long i=(s);i<(long long)(n);i++)
#define bitrep(i,s,n) for(long long i=(s);i<(1LL<<(n));i++)
#define bitcheck(bit,i) (bit)&(1LL<<(i))
#define Maxe(x) *max_element((x).begin(),(x).end())
#define Mine(x) *min_element((x).begin(),(x).end())
#define Size(x) ((long long)(x).size())
#define Lin(s) getline(cin,(s))

//Yes,No
void Yes(bool a){cout<<(a?"Yes":"No")<<endl;}
void YES(bool a){cout<<(a?"YES":"NO")<<endl;}

//MAX,MIN
template<class T,class U> auto max(T a,U b){return a>b?a:b;}
template<class T,class U> auto min(T a,U b){return a<b?a:b;}

//最大公約数,最小公倍数
long long gcd(long long a,long long b){return b?gcd(b,a%b):a;}
long long lcm(long long a,long long b){return a/gcd(a,b)*b;}

//切り上げ除算
long long cutup(long long a,long long b){return (a+b-1)/b;}

//累乗
template<typename t>
constexpr t my_pow(t a,long long b){
    if(b==0)return 1;
    if(a==0)return 0;
    t x=1;
    while(b>0){
        if(b&1LL)x*=a;
        a*=a;
        b>>=1LL;
    }
    return x;
}
#define pow my_pow

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

//組み合わせ O(r)
template<typename t>
constexpr t nCr(t n,long long r){
    if(r==0)return 1;
    if(n==0)return 0;
    if(n<r)return 0;
    t x=1;
    for(long long i=1;i<=r;i++){
        x*=n-i+1;
        x/=i;
    }
    return x;
}

//BIT
//初期値はa_1=a_2=...=a_n=0
//add(i,x):a_i+=xとする
//sum(i):a_1+a_2+...+a_iを計算する
template <typename T>
struct BIT{
    int n;// 配列の要素数(数列の要素数+1)
    vector<T> bit;// データの格納先
    BIT(int n_) : n(n_ + 1), bit(n, 0) {}
    void add(int i, T x) {
        for (int idx = i; idx < n; idx += (idx & -idx)) {
            bit[idx] += x;
        }
    }
    T sum(int i) {
        T s(0);
        for (int idx = i; idx > 0; idx -= (idx & -idx)) {
            s += bit[idx];
        }
        return s;
    }
};

//main関数
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n,q;
    string s;
    cin>>n>>s>>q;
    vector<BIT<int>> C(26,BIT<int>(n+1));
    rep(i,n){
        C[s[i]-'a'].add(i+1,1);
    }
    rep(i,q){
        int a;
        cin>>a;
        if(a==1){
            int b;
            char c;
            cin>>b>>c;
            C[s[b-1]-'a'].add(b,-1);
            C[c-'a'].add(b,1);
            s[b-1]=c;
        }else{
            int l,r;
            cin>>l>>r;
            ll res=0;
            rep(j,26){
                if(C[j].sum(r)-C[j].sum(l-1)>0)res++;
            }
            cout<<res<<"\n";
        }
    }
}

Measured memory_bytes: 56536