Buggy python submission (verdict: Runtime Error):
n,x,m=map(int,input().split())
a=[]
mod_check_list = [False for _ in range(M)]
a.append(x*x%m)
ind=0
s=0
for i in range(m):
    t=a[i]*a[i]%m
    if mod_check_list[t]:
        ind=a.index(t)
        break
    mod_check_list[t] = True
    a.append(t)
s=sum(a[ind:])
l=len(a)-ind
loop_times = (n-1-ind)//l
answer=loop_times*s
for i in range((n-1-ind)%l):
    answer+=a[i+ind]
print(answer+x+sum(a[:ind]))

Fixed submission:
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + sum(mod_list[:min(counter, N - 1)])
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:N - 1])
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
n,x,m=map(int,input().split())
a=[]
a.append(x*x%m)
ind=0
s=0
for i in range(m):
    t=a[i]*a[i]%m
    if a.count(t)==0:
        a.append(t)
    else:
        ind=a.index(t)
        break
s=sum(a[ind:])
l=len(a)-ind
loop_times = (n-1-ind)//l
answer=loop_times*s
for i in range((n-1-ind)%l):
    answer+=a[i+ind]
print(answer+x+sum(a[:ind]))

Fixed submission:
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + sum(mod_list[:min(counter, N - 1)])
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:N - 1])
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + sum(mod_list[:min(counter, N - 1)])
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:counter])
        print(aa)
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)

Fixed submission:
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + sum(mod_list[:min(counter, N - 1)])
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:N - 1])
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)

Buggy python submission (verdict: Runtime Error):
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + mod_list[:min(counter, N - 1)]
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:counter])
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)

Fixed submission:
# -*- coding: utf-8 -*-
N, X, M = map(int, input().split())

mod_check_list = [False for _ in range(M)]
mod_list = [(X ** 2) % M]
counter = 1
mod_sum = (X ** 2) % M
last_mod = 0
for i in range(M):
    now_mod = (mod_list[-1] ** 2) % M
    if mod_check_list[now_mod]:
        last_mod = now_mod
        break
    mod_check_list[now_mod] = True
    mod_list.append(now_mod)
    counter += 1
    mod_sum += now_mod

loop_start_idx = 0
for i in range(counter):
    if last_mod == mod_list[i]:
        loop_start_idx = i
        break

loop_list = mod_list[loop_start_idx:]
loop_num = counter - loop_start_idx
ans = 0
if mod_list[-1] == 0:
    ans = X + sum(mod_list[:min(counter, N - 1)])
else:
    if (N - 1) <= counter:
        ans = X + sum(mod_list[:N - 1])
    else:
        ans += X + mod_sum
        N -= (counter + 1)
        ans += sum(loop_list) * (N // loop_num) + sum(loop_list[:N % loop_num])
print(ans)