Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        dict[_s].pop(bisect.bisect_left(dict[_s], first))
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Runtime Error):
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        _s = s[first]
        first = int(first)
        first -= 1
        dict[_s].pop(bisect.bisect_left(dict[_s], first))
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for a in alpha:
            ls = dict[a]
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        dict[s[first]].pop(bisect.bisect_left(dict[s[first]], first))
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(input())
s = list(input())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(input())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for a in alpha:
            ls = dict[a]
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        dict[s[first]].pop(bisect.bisect_left(dict[s[first]], first))
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(input())
s = list(input())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(input())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for a in alpha:
            ls = dict[a]
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        dict[s[first]].pop(bisect.bisect_left(dict[s[first]], first))
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
import bisect
n = int(input())
s = list(input())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(input())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for a in alpha:
            ls = dict[a]
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        dict[s[first]].remove(first)
        s[first] = last
        bisect.insort_left(dict[last], first)

Fixed submission:
import sys
import bisect
n = int(sys.stdin.readline().strip())
s = list(sys.stdin.readline().strip())
alpha = "abcdefghijklmnopqrstuvwxyz"
dict = {i:[] for i in alpha}
for i, _s in enumerate(s):
    dict[_s].append(i)
q = int(sys.stdin.readline().strip())
for i in range(q):
    type, first, last = [i for i in sys.stdin.readline().split()]
    if type == "2":
        first = int(first)
        last = int(last)
        first -= 1
        last -= 1
        cnt = 0
        for ls in dict.values():
            if bisect.bisect_left(ls, first) != bisect.bisect_right(ls, last):
                cnt += 1
        print(cnt)
    else:
        first = int(first)
        first -= 1
        _s = s[first]
        if _s == last:
            continue
        del dict[_s][(bisect.bisect_left(dict[_s], first))]
        s[first] = last
        bisect.insort_left(dict[last], first)