import sys
def input(): return sys.stdin.readline().rstrip()

# ライブラリ参照https://atcoder.jp/contests/practice2/submissions/16580070
class SegmentTree:

    __slots__ = ["func", "e", "original_size", "n", "data"]

    def __init__(self, length_or_list, func, e):
        self.func = func
        self.e = e
        if isinstance(length_or_list, int):
            self.original_size = length_or_list
            self.n = 1 << ((length_or_list - 1).bit_length())
            self.data = [self.e] * self.n
        else:
            self.original_size = len(length_or_list)
            self.n = 1 << ((self.original_size - 1).bit_length())
            self.data = [self.e] * self.n + length_or_list + \
                [self.e] * (self.n - self.original_size)
            for i in range(self.n-1, 0, -1):
                self.data[i] = self.func(self.data[2*i], self.data[2*i+1])

    def replace(self, index, value):
        index += self.n
        self.data[index] = value
        index //= 2
        while index > 0:
            self.data[index] = self.func(
                self.data[2*index], self.data[2*index+1])
            index //= 2

    def folded(self, l, r):
        left_folded = self.e
        right_folded = self.e
        l += self.n
        r += self.n
        while l < r:
            if l % 2:
                left_folded = self.func(left_folded, self.data[l])
                l += 1
            if r % 2:
                r -= 1
                right_folded = self.func(self.data[r], right_folded)
            l //= 2
            r //= 2
        return self.func(left_folded, right_folded)

    def all_folded(self):
        return self.data[1]

    def __getitem__(self, index):
        return self.data[self.n + index]

    def max_right(self, l, f):
        # assert f(self.e)
        if l >= self.original_size:
            return self.original_size
        l += self.n
        left_folded = self.e
        while True:
            # l //= l & -l
            while l % 2 == 0:
                l //= 2
            if not f(self.func(left_folded, self.data[l])):
                while l < self.n:
                    l *= 2
                    if f(self.func(left_folded, self.data[l])):
                        left_folded = self.func(left_folded, self.data[l])
                        l += 1
                return l - self.n
            left_folded = self.func(left_folded, self.data[l])
            l += 1
            if l == l & -l:
                break
        return self.original_size

    # 未verify
    def min_left(self, r, f):
        # assert f(self.e)
        if r == 0:
            return 0
        r += self.n
        right_folded = self.e
        while True:
            r //= r & -r
            if not f(self.func(self.data[r], right_folded)):
                while r < self.n:
                    r = 2 * r + 1
                    if f(self.func(self.data[r], right_folded)):
                        right_folded = self.func(self.data[r], right_folded)
                        r -= 1
                return r + 1 - self.n
            if r == r & -r:
                break
        return 0


def orr(x, y):
    return x | y


def main():
    N = int(input())
    S = input()
    S = list(map(lambda c: 2**(ord(c) - ord('a')), list(S)))
    Q = int(input())
    seg = SegmentTree(S, orr, 0)
    for _ in range(Q):
        num, x, y = input().split()
        if num == '1':
            seg.replace(int(x)-1, 2**(ord(y) - ord('a')))
        else:
            bits = seg.folded(int(x)-1, int(y))
            print(sum(map(int, list(bin(bits))[2:])))


if __name__ == '__main__':
    main()

Measured memory_bytes: 54224