# Problem: Sums with Step of 3

The next sample exam problem is about calculating 3 sums, holding the numbers from given sequence, staying at certain positions with step 3.

## Video: Sums with Step of 3

Watch the video lesson about solving the "Sums with Step of 3" problem: https://youtu.be/bRHFuNNBmZc.

## Problem Description

We are given **n** integers: **a1, a2, …, an**. Calculate the sums:

**sum1 = a1 + a4 + a7**+ … (the numbers are summed, starting from the first one with step of 3).**sum2 = a2 + a5 + a8**+ … (the numbers are summed, starting from the second one with step of 3).**sum3 = a3 + a6 + a9**+ … (the numbers are summed, starting from the third one with step of 3).

## Input

The input data is read from the console. The first line holds an integer **n (0 ≤ n ≤ 1000)**. On the next **n** lines we are given **n** integers in the range [**-1000 … 1000**]: **a1, a2, …, an**.

## Output

On the console we should print 3 lines containing the 3 sums in a format such as in the example.

## Sample Input and Output

Input | Output | Input | Output | Input | Output |
---|---|---|---|---|---|

2 3 5 |
sum1 = 3 sum2 = 5 sum3 = 0 |
4 7 -2 6 12 |
sum1 = 19 sum2 = -2 sum3 = 6 |
5 3 5 2 7 8 |
sum1 = 10 sum2 = 13 sum3 = 2 |

## Reading the Input Data

We will take **the count of numbers** from the console and declare **starting values** of the three sums.

Since we do not know in advance how many numbers we will process, we will take them one at a time in **a loop** which will be repeated **n times** and we will process them in the body of the loop.

## Allocating Numbers and Printing Results

To find out in which of **the three sums** we need to add the number, we will divide its **sequence number into three** and we will use the remainder. We will use the variable ** i**, which tracks

**the number of runs**of the loop, in order to find out which sequence number we are at. When the remainder of

**is**

`i/3`

**zero**, it means we will add this number to

**the first**sum, when it is

**1**to the

**second**one, and when it is

**2**to

**the third**one.

Finally, we will print the result on the console in the required **format**.

## Testing in the Judge System

Test your solution here: https://judge.softuni.org/Contests/Practice/Index/516#6.