Buggy python submission (verdict: Time Limit Exceeded):
import bisect

n = int(input())
s = input()
q = int(input())

alpha_map = {chr(i):[] for i in range(97,123)}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s = s[:y-1]+z+s[y:]
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)

Fixed submission:
import bisect

n = int(input())
s = list(input())
q = int(input())

alpha_map = {chr(i):[] for i in range(97,123)}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s[y-1] = z
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)

Buggy python submission (verdict: Runtime Error):
import bisect

n = int(input())
s = input()
q = int(input())

alpha_map = {i:[] for i in alpha}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s = s[:y-1]+z+s[y:]
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)

Fixed submission:
import bisect

n = int(input())
s = list(input())
q = int(input())

alpha_map = {chr(i):[] for i in range(97,123)}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s[y-1] = z
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)

Buggy python submission (verdict: Time Limit Exceeded):
import bisect

n = int(input())
s = input()
q = int(input())

alpha = [chr(i) for i in range(97,123)]
alpha_map = {i:[] for i in alpha}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s = s[:y-1]+z+s[y:]
    else:
        count = 0
        for i in alpha:
            if len(alpha_map[i]) > 0:
                idx = bisect.bisect_left(alpha_map[i],int(y))
                if idx < len(alpha_map[i]) and alpha_map[i][idx] <= int(z):
                    count += 1
        print(count)

Fixed submission:
import bisect

n = int(input())
s = list(input())
q = int(input())

alpha_map = {chr(i):[] for i in range(97,123)}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s[y-1] = z
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter

n = int(input())
s = input()
q = int(input())
Q = [list(map(str,input().split())) for _ in range(q)]

for x,y,z in Q:
    if int(x) == 1:
        s = s[:int(y)-1]+z+s[int(y):]
    else:
        c = Counter(s[int(y)-1:int(z)])
        print(len(c.keys()))

Fixed submission:
import bisect

n = int(input())
s = list(input())
q = int(input())

alpha_map = {chr(i):[] for i in range(97,123)}
for i,c in enumerate(s):
    bisect.insort(alpha_map[c],i+1)
    
for _ in range(q):
    x,y,z = map(str,input().split())
    if int(x) == 1:
        y = int(y)
        bef = s[y-1]
        if bef == z:
            continue
        alpha_map[bef].pop(bisect.bisect_left(alpha_map[bef],y))
        bisect.insort(alpha_map[z],y)
        s[y-1] = z
    else:
        count = 0
        for i,j in alpha_map.items():
            idx = bisect.bisect_left(j,int(y))
            if idx < len(j) and j[idx] <= int(z):
                    count += 1
        print(count)