#!python3

import sys

iim = lambda: map(int, input().rstrip().split())

def popcnt2(n):
    a = (
        0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
    )
    ans = 0
    while n:
        ans += a[n&0xff]
        n >>= 8
    return ans

def resolve():
    N = int(input())
    S = list(input())
    Q = int(input())

    c0 = ord('a')
    smap = [1<<(i-c0) for i in range(c0, ord('z')+1)]

    T = [0]*N + [smap[ord(S[i])-c0] for i in range(N)]

    for i in range(N-1, 0, -1):
        i2 = i << 1
        T[i] = T[i2] | T[i2|1]

    ans = []
    #print(T)
    for cmd, i, j in (line.split() for line in sys.stdin.read().split("\n")):
        i = int(i) - 1
        if cmd == "1":
            if S[i] == j:
                continue

            S[i] = j
            i0 = N + i
            T[i0] = smap[ord(j)-c0]
            while i0 > 1:
                i0 = i0 >> 1
                T[i0] = T[i0+i0] | T[i0-~i0]
        elif cmd == "2":
            i += N
            j = int(j) + N

            d1 = 0
            while i < j:
                if i & 1:
                    d1 |= T[i]
                    i += 1
                if j & 1:
                    j -= 1
                    d1 |= T[j]

                i >>= 1; j >>=1

            ans.append(popcnt2(d1))

    print(*ans, sep="\n")

if __name__ == "__main__":
    resolve()


### FIXED CODE ###

#!python3

import sys

from bisect import bisect, insort_left

iim = lambda: map(int, input().rstrip().split())

def resolve():
    N = int(input())
    S = list(input())
    Q = int(input())

    c0 = ord('a')
    S1 = [[] for i in range(26)]
    for i, c1 in enumerate(S):
        ci = ord(c1) - c0
        S1[ci].append(i)

    ans = []
    for cmd, i, j in (line.split() for line in sys.stdin):
        i = int(i) - 1
        if cmd == "1":
            if S[i] == j:
                continue

            c1 = ord(S[i]) - c0
            s1 = S1[c1]
            s1.pop(bisect(s1, i)-1)
            S[i] = j
            c1 = ord(j) - c0
            insort_left(S1[c1], i)
        elif cmd == "2":
            j = int(j) - 1
            num = 0

            for s1 in S1:
                ls = len(s1)
                k = bisect(s1, i-1, 0, ls)

                if k == ls:
                    continue
                if i <= s1[k] <= j:
                    num += 1

            ans.append(num)

    print(*ans, sep="\n")

if __name__ == "__main__":
    resolve()