Buggy python submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline

Days = int(input())
C = list(map(int, input().split())) # 満足度低下
Ss = [list(map(int, input().split())) for _ in range(Days)]
# Ss[d][i]: d日目にiを開催したときの満足度
T = [int(input()) for _ in range(Days)] # 開催するコンテスト
Q = int(input())
Query = [list(map(int, input().split())) for _ in range(Q)]

INF = 10**18

def outputToScore(T):
    last = [0]*26
    used = [[] for _ in range(26)]
    satisfied = 0
    for d, t in enumerate(T):
        t -= 1; d += 1
        satisfied += Ss[d-1][t]
        used[t].append(d)
        last[t] = d
        for i, c in enumerate(C):
            satisfied -= c*(d-last[i])
        # print(satisfied)
    return satisfied, used

Satisfied, Used = outputToScore(T)
for d, aft in Query:
    aft -= 1
    bef = T[d-1]-1
    deltaSatis = Ss[d-1][aft] - Ss[d-1][bef]
    # d日目のコンテストをbefからaftに変える

    # bi-1 -> bi -> bi+1 を bi-1 -> bi+1
    befind = Used[bef].index(d)
    befday0 = 0 if befind == 0 else Used[bef][befind-1]
    befday2 = Days+1 if befind == len(Used[bef])-1 else Used[bef][befind+1]
    
    befd01 = d - befday0
    befd12 = befday2 - d
    befd02 = befday2-befday0
    deltaSatis -= C[bef]*(befd02*(befd02-1)//2) - C[bef]*(befd01*(befd01-1)//2 + befd12*(befd12-1)//2)

    # ai -> ai+1 を ai -> (insert) -> ai+1
    if len(Used[aft]) > 0:
        aftday0 = 0
        aftday2 = Days+1
        newaft = []
        for i,a in enumerate(Used[aft]):
            if a < d:
                aftday0 = a
            elif aftday2 == Days+1:
                newaft.append(d)
                aftday2 = a
            newaft.append(a)
        aftd01 = d - aftday0
        aftd12 = aftday2 - d
        aftd02 = aftd01 + aftd12
        deltaSatis += C[aft]*(aftd02*(aftd02-1)//2) - C[aft]*(aftd01*(aftd01-1)//2 + aftd12*(aftd12-1)//2)
    else:
        newaft = [d]
        d01 = d
        d12 = Days+1 - d
        deltaSatis += C[aft] * Days*(Days+1)//2 - C[aft]*(d01*(d01-1)//2 + d12*(d12-1)//2)

    Used[bef].remove(d)
    Used[aft] = newaft
    T[d-1] = aft+1
    Satisfied += deltaSatis
    print(Satisfied)



Fixed submission:
import sys
input = sys.stdin.readline

Days = int(input())
C = list(map(int, input().split())) # 満足度低下
Ss = [list(map(int, input().split())) for _ in range(Days)]
# Ss[d][i]: d日目にiを開催したときの満足度
T = [int(input()) for _ in range(Days)] # 開催するコンテスト
Q = int(input())
Query = [list(map(int, input().split())) for _ in range(Q)]

INF = 10**18

def outputToScore(T):
    last = [0]*26
    used = [[] for _ in range(26)]
    satisfied = 0
    for d, t in enumerate(T):
        t -= 1; d += 1
        satisfied += Ss[d-1][t]
        used[t].append(d)
        last[t] = d
        for i, c in enumerate(C):
            satisfied -= c*(d-last[i])
        # print(satisfied)
    return satisfied, used

Satisfied, Used = outputToScore(T)
for d, aft in Query:
    aft -= 1
    bef = T[d-1]-1
    deltaSatis = Ss[d-1][aft] - Ss[d-1][bef]
    # d日目のコンテストをbefからaftに変える

    # bi-1 -> bi -> bi+1 を bi-1 -> bi+1
    befind = Used[bef].index(d)
    befday0 = 0 if befind == 0 else Used[bef][befind-1]
    befday2 = Days+1 if befind == len(Used[bef])-1 else Used[bef][befind+1]
    
    befd01 = d - befday0
    befd12 = befday2 - d
    befd02 = befday2-befday0
    deltaSatis -= C[bef]*(befd02*(befd02-1)//2) - C[bef]*(befd01*(befd01-1)//2 + befd12*(befd12-1)//2)

    # ai -> ai+1 を ai -> (insert) -> ai+1
    if len(Used[aft]) > 0:
        aftday0 = 0
        aftday2 = Days+1
        newaft = []
        for i,a in enumerate(Used[aft]):
            if a < d:
                aftday0 = a
            elif aftday2 == Days+1:
                newaft.append(d)
                aftday2 = a
            newaft.append(a)
        if aftday2 == Days+1:
            newaft.append(d)
        aftd01 = d - aftday0
        aftd12 = aftday2 - d
        aftd02 = aftd01 + aftd12
        deltaSatis += C[aft]*(aftd02*(aftd02-1)//2) - C[aft]*(aftd01*(aftd01-1)//2 + aftd12*(aftd12-1)//2)
    else:
        newaft = [d]
        d01 = d
        d12 = Days+1 - d
        deltaSatis += C[aft] * Days*(Days+1)//2 - C[aft]*(d01*(d01-1)//2 + d12*(d12-1)//2)

    Used[bef].remove(d)
    Used[aft] = newaft
    T[d-1] = aft+1
    Satisfied += deltaSatis
    print(Satisfied)

Buggy python submission (verdict: Runtime Error):
from bisect import bisect_right, bisect_left
# instead of AVLTree
class BITbisect():
    def __init__(self, InputProbNumbers):
        # 座圧
        self.ind_to_co = [-10**18]
        self.co_to_ind = {}
        for ind, num in enumerate(InputProbNumbers):
            self.ind_to_co.append(num)
            self.co_to_ind[num] = ind+1
        self.max = len(self.co_to_ind)
        self.data = [0]*(self.max+1)
    
    def __str__(self):
        retList = []
        for i in range(1, self.max+1):
            x = self.ind_to_co[i]
            if self.count(x):
                c = self.count(x)
                for _ in range(c):
                    retList.append(x)
        return "[" + ", ".join([str(a) for a in retList]) + "]"
    
    def __getitem__(self, key):
        key += 1
        s = 0
        ind = 0
        l = self.max.bit_length()
        for i in reversed(range(l)):
            if ind + (1<<i) <= self.max:
                if s + self.data[ind+(1<<i)] < key:
                    s += self.data[ind+(1<<i)]
                    ind += (1<<i)
        if ind == self.max or key < 0:
            raise IndexError("BIT index out of range")
        return self.ind_to_co[ind+1]
    
    def __len__(self):
        return self._query_sum(self.max)
    
    def __contains__(self, num):
        if not num in self.co_to_ind:
            return False
        return self.count(num) > 0
    
    # 0からiまでの区間和
    # 左に進んでいく
    def _query_sum(self, i):
        s = 0
        while i > 0:
            s += self.data[i]
            i -= i & -i
        return s

    # i番目の要素にxを足す
    # 上に登っていく
    def _add(self, i, x):
        while i <= self.max:
            self.data[i] += x
            i += i & -i
    
    # 値xを挿入
    def push(self, x):
        if not x in self.co_to_ind:
            raise KeyError("The pushing number didnt initialized")
        self._add(self.co_to_ind[x], 1)
            
    # 値xを削除
    def delete(self, x):
        if not x in self.co_to_ind:
            raise KeyError("The deleting number didnt initialized")
        if self.count(x) <= 0:
            raise ValueError("The deleting number doesnt exist")
        self._add(self.co_to_ind[x], -1)

    # 要素xの個数
    def count(self, x):
        return self._query_sum(self.co_to_ind[x]) - self._query_sum(self.co_to_ind[x]-1)
    
    # 値xを超える最低ind
    def bisect_right(self, x):
        if x in self.co_to_ind:
            i = self.co_to_ind[x]
        else:
            i = bisect_right(self.ind_to_co, x) - 1
        return self._query_sum(i)

    # 値xを下回る最低ind
    def bisect_left(self, x):
        if x in self.co_to_ind:
            i = self.co_to_ind[x]
        else:
            i = bisect_left(self.ind_to_co, x)
        if i == 1:
            return 0
        return self._query_sum(i-1)

import sys
input = sys.stdin.readline

Days = int(input())
C = list(map(int, input().split())) # 満足度低下
Ss = [list(map(int, input().split())) for _ in range(Days)]
# Ss[d][i]: d日目にiを開催したときの満足度
T = [int(input()) for _ in range(Days)] # 開催するコンテスト
Q = int(input())
Query = [list(map(int, input().split())) for _ in range(Q)]

INF = 10**18

def outputToScore(T):
    last = [0]*26
    used = [BITbisect(list(range(Days+1))) for _ in range(26)]
    satisfied = 0
    for d, t in enumerate(T):
        t -= 1; d += 1
        satisfied += Ss[d-1][t]
        used[t].push(d)
        last[t] = d
        for i, c in enumerate(C):
            satisfied -= c*(d-last[i])
        # print(satisfied)
    return satisfied, used

Satisfied, Used = outputToScore(T)
for d, aft in Query:
    aft -= 1
    bef = T[d-1]-1
    deltaSatis = Ss[d-1][aft] - Ss[d-1][bef]
    # d日目のコンテストをbefからaftに変える
    befind = Used[bef].bisect_left(d)
    aftind = Used[aft].bisect_left(d)
    #print(d)
    #print(Used[bef], bef)
    #print(Used[aft], aft)
    # bi-1 -> bi -> bi+1 を bi-1 -> bi+1
    befday0 = 0
    befday2 = Days+1
    if befind > 0:
        befday0 = Used[bef][befind-1]
    if befind < len(Used[bef])-1:
        befday2 = Used[bef][befind+1]
    befd01 = d - befday0
    befd12 = befday2 - d
    befd02 = befday2-befday0
    deltaSatis -= C[bef]*(befd02*(befd02-1)//2) - C[bef]*(befd01*(befd01-1)//2 + befd12*(befd12-1)//2)

    # ai -> ai+1 を ai -> (insert) -> ai+1
    if len(Used[aft]) > 0:
        aftday0 = 0
        aftday2 = Used[aft][aftind]
        if aftind > 0:
            aftday0 = Used[aft][aftind-1]
        aftd01 = d - aftday0
        aftd12 = aftday2 - d
        aftd02 = aftd01 + aftd12
        deltaSatis += C[aft]*(aftd02*(aftd02-1)//2) - C[aft]*(aftd01*(aftd01-1)//2 + aftd12*(aftd12-1)//2)
    else:
        d01 = d
        d12 = Days+1 - d
        deltaSatis += C[aft] * Days*(Days+1)//2 - C[aft]*(d01*(d01-1)//2 + d12*(d12-1)//2)

    Used[bef].delete(d)
    Used[aft].push(d)
    T[d-1] = aft+1
    Satisfied += deltaSatis
    print(Satisfied)



Fixed submission:
import sys
input = sys.stdin.readline

Days = int(input())
C = list(map(int, input().split())) # 満足度低下
Ss = [list(map(int, input().split())) for _ in range(Days)]
# Ss[d][i]: d日目にiを開催したときの満足度
T = [int(input()) for _ in range(Days)] # 開催するコンテスト
Q = int(input())
Query = [list(map(int, input().split())) for _ in range(Q)]

INF = 10**18

def outputToScore(T):
    last = [0]*26
    used = [[] for _ in range(26)]
    satisfied = 0
    for d, t in enumerate(T):
        t -= 1; d += 1
        satisfied += Ss[d-1][t]
        used[t].append(d)
        last[t] = d
        for i, c in enumerate(C):
            satisfied -= c*(d-last[i])
        # print(satisfied)
    return satisfied, used

Satisfied, Used = outputToScore(T)
for d, aft in Query:
    aft -= 1
    bef = T[d-1]-1
    deltaSatis = Ss[d-1][aft] - Ss[d-1][bef]
    # d日目のコンテストをbefからaftに変える

    # bi-1 -> bi -> bi+1 を bi-1 -> bi+1
    befind = Used[bef].index(d)
    befday0 = 0 if befind == 0 else Used[bef][befind-1]
    befday2 = Days+1 if befind == len(Used[bef])-1 else Used[bef][befind+1]
    
    befd01 = d - befday0
    befd12 = befday2 - d
    befd02 = befday2-befday0
    deltaSatis -= C[bef]*(befd02*(befd02-1)//2) - C[bef]*(befd01*(befd01-1)//2 + befd12*(befd12-1)//2)

    # ai -> ai+1 を ai -> (insert) -> ai+1
    if len(Used[aft]) > 0:
        aftday0 = 0
        aftday2 = Days+1
        newaft = []
        for i,a in enumerate(Used[aft]):
            if a < d:
                aftday0 = a
            elif aftday2 == Days+1:
                newaft.append(d)
                aftday2 = a
            newaft.append(a)
        if aftday2 == Days+1:
            newaft.append(d)
        aftd01 = d - aftday0
        aftd12 = aftday2 - d
        aftd02 = aftd01 + aftd12
        deltaSatis += C[aft]*(aftd02*(aftd02-1)//2) - C[aft]*(aftd01*(aftd01-1)//2 + aftd12*(aftd12-1)//2)
    else:
        newaft = [d]
        d01 = d
        d12 = Days+1 - d
        deltaSatis += C[aft] * Days*(Days+1)//2 - C[aft]*(d01*(d01-1)//2 + d12*(d12-1)//2)

    Used[bef].remove(d)
    Used[aft] = newaft
    T[d-1] = aft+1
    Satisfied += deltaSatis
    print(Satisfied)