#include <bits/stdc++.h>

#define F first
#define S second
#define MP make_pair
#define pb push_back
#define all(a) a.begin(), a.end()
#define lcm( a, b ) (a)/__gcd((a),(b))*(b)
#define endl '\n'

using namespace std;

typedef long long LL;
typedef pair< int, int > P;
typedef pair< LL, LL > LP;

static const int INF = INT_MAX;
static const LL LINF = LLONG_MAX;
static const int MIN = INT_MIN;
static const LL LMIN = LLONG_MIN;
static const int MOD = 1000000007;
static const int SIZE = 200005;

const int dx[] = {0, -1, 1, 0};
const int dy[] = {-1, 0, 0, 1};

LL fac[SIZE], finv[SIZE], inv[SIZE];
void combInit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for( int i = 2; i < SIZE; ++i ) {
        fac[i] = (fac[i - 1] * i) % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = (finv[i - 1] * inv[i]) % MOD;

    }
}

LL comb(int n, int k) {
    if( n < k ) return 0;
    if( n < 0 || k < 0 ) return 0;
    return (fac[n] * (finv[k] * finv[n - k] % MOD)) % MOD;

}

vector< int > Div( int n ) {
    vector< int > ret;
    for( int i = 1; i * i <= n; ++i ) {
        if( n % i == 0 ) {
            ret.pb( i );

            if( i * i != n ) ret.pb( n / i );
        }
    }
    sort( all( ret ) );
    return ret;
}

int chcnt[1<<20][26];
string s;
int ch[26];
struct SegmentTree {
    private:
        int n;
        vector< int > v;

    public:
        SegmentTree(string str) {
            int sz = str.size();
            n = 1;
            while( n < sz ) n <<= 1;
            v.resize(2 * n - 1, INF);

            for( int i = 0; i < sz; ++i ) {
                chcnt[i + n - 1][str[i] - 'a'] = 1;

            }
            for( int i = n - 2; i >= 0; --i ) {
                for( int j = 0; j < 26; ++j ) {
                    chcnt[i][j] = chcnt[i * 2 + 1][j] + chcnt[i * 2 + 2][j];

                }
            }
        }

        void Update(int x, int v) {
            int t = s[x];
            s[x] = v;
            x += n - 1;
            chcnt[x][t - 'a'] = 0;
            chcnt[x][v - 'a'] = 1;
            while( x > 0 ) {
                x = (x - 1) / 2;
                chcnt[x][t - 'a']--;
                chcnt[x][v - 'a']++;

            }
        }

        void query(int a, int b, int k, int l, int r = -1) {
            if( r < 0 ) {
                r = n;

            }
            if( r <= a || b <= l ) return;
            if( a <= l && r <= b ) {
                for( int i = 0; i < 26; ++i ) {
                    ch[i] += chcnt[k][i];

                }
                return;
            }

            query(a, b, 2 * k + 1, l, (l + r) / 2);
            query(a, b, 2 * k + 2, (l + r) / 2, r);
            return;
        }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;
    cin >> s;

    SegmentTree seg(s);
    int q;
    cin >> q;
    while( q-- ) {
        int a, b;
        cin >> a >> b;
        if( a == 1 ) {
            char c;
            cin >> c;
            seg.Update(b - 1, c);

        } else {
            int c;
            cin >> c;
            seg.query(b - 1, c, 0, 0, -1);
            int cnt = 0;
            for( int i = 0; i < 26; ++i ) {
                if( ch[i] != 0 ) {
                    ++cnt;
                    ch[i] = 0;

                }
            }
            cout << cnt << endl;

        }
    }
    return 0;
}



Measured memory_bytes: 109852