466C - Number of Ways - CodeForces Solution

length = int(input())
nums = [int(x) for x in input().split()]
summ = sum(nums)
third = summ // 3
if summ % 3 == 0 and third != 0 and length > 2:
    
            sum_temp = 0
    counter = 0
    for i in range(length):
        sum_temp += nums[i]
        if sum_temp == third:
            counter = i + 1
            break
    
    if counter == length:
        print(0)
    else:
        
                                                sum_temp = 0
        zero_count1 = 1
        negative_sum1 = 0
        negative = True
        adder = 0
        for i in range(counter,length):
            sum_temp += nums[i]
            if nums[i] < 0 and negative:
                negative_sum1 += nums[i]
                if abs(negative_sum1) == third:
                    adder = 1
                    negative = False
            else:
                negative = False
            if sum_temp == third:
                counter = i + 1
                break
            elif sum_temp == 0:
                zero_count1 += 1
        
        
        if  counter == length:
            print(0)
        else:
                                                            sum_temp = 0
            zero_count2 = 1
            negative = True
            for i in range(counter,length):
                sum_temp += nums[i]
                if nums[i] < 0 and negative:
                    negative_sum1 += nums[i]
                    if abs(negative_sum1) == third:
                        adder += 1
                        negative = False
                else:
                    negative = False
                if sum_temp == 0:
                    zero_count2 += 1
            
            if sum_temp != third:
                print(0)
            else:
                                print(zero_count1 * zero_count2 + adder)

elif third == 0 and length > 2:
    
            temp_sum = 0
    zero_counter = -2
    for i in range(length):
        temp_sum += nums[i]
        if temp_sum == 0:
            zero_counter += 1
    
    print(int(zero_counter/2*(zero_counter+1)))
    
else:
    print(0)