In the previous article, we have discussed Python Program to Find Sum of Series 1+1/3+1/5+1/7+…..1/(N+2)

Given a number N and the task is to find the sum of the given series **(1-2+3-4+5…+N)** for the given number in Python.

**Examples:**

**Example1:**

**Input:**

Given Number = 20

**Output:**

The total sum of the series till the given number { 20 } = -10

**Example2:**

**Input:**

Given Number = 7

**Output:**

The total sum of the series till the given number { 7 } = 4

## Program to Find Sum of Series 1-2+3-4+5…+N in Python

Below are the ways to find the sum of the given series** (1-2+3-4+5…+N)** for the given number in Python:

### Method #1: Using For Loop (Static Input)

**Approach:**

- Give the number N as static input and store it in a variable.
- Take a variable say resltsum which gives the sum of the given series till N and initialize its value to 0.
- Loop from 1 to the given number using the for loop.
- Inside the loop, check if the value of iterator modulus 2 is equal to zero(even condition) or not using the if conditional statement.
- If the statement is True, then subtract the iterator value from the above-declared
**resltsum.** - Store it in the same variable
**resltsum.** - Else if the statement is False, then add the iterator value to the above-declared
**resltsum.** - Store it in the same variable
**resltsum.** - Print the
**resltsum**value which is the result of the series till the given Number N. - The Exit of the Program.

**Below is the implementation:**

# Give the number N as static input and store it in a variable. gvn_numb = 20 # Take a variable say resltsum which gives the sum of the given series till N and # initialize its value to 0. resltsum = 0 # Loop from 1 to the given number using the for loop. for itr in range(1, gvn_numb+1): # Inside the loop, check if the value of iterator modulus 2 is equal to zero(even condition) # or not using the if conditional statement. if itr % 2 == 0: # If the statement is True, then subtract the iterator value from the above-declared # resltsum. # Store it in the same variable resltsum. resltsum -= itr else: # Else if the statement is False, then add the iterator value to the above-declared # resltsum. # Store it in the same variable resltsum. resltsum += itr # Print the resltsum value which is the result of the series till the given Number N. print( "The total sum of the series till the given number {", gvn_numb, "} = ", resltsum)

**Output:**

The total sum of the series till the given number { 20 } = -10

### Method #2: Using For loop (User Input)

**Approach:**

- Give the number N as user input using the int(input()) function and store it in a variable.
- Take a variable say resltsum which gives the sum of the given series till N and initialize its value to 0.
- Loop from 1 to the given number using the for loop.
- Inside the loop, check if the value of iterator modulus 2 is equal to zero(even condition) or not using the if conditional statement.
- If the statement is True, then subtract the iterator value from the above-declared
**resltsum.** - Store it in the same variable
**resltsum.** - Else if the statement is False, then add the iterator value to the above-declared
**resltsum.** - Store it in the same variable
**resltsum.** - Print the
**resltsum**value which is the result of the series till the given Number N. - The Exit of the Program.

**Below is the implementation:**

# Give the number N as user input using the int(input()) function and # store it in a variable. gvn_numb = int(input("Enter some Random Number = ")) # Take a variable say resltsum which gives the sum of the given series till N and # initialize its value to 0. resltsum = 0 # Loop from 1 to the given number using the for loop. for itr in range(1, gvn_numb+1): # Inside the loop, check if the value of iterator modulus 2 is equal to zero(even condition) # or not using the if conditional statement. if itr % 2 == 0: # If the statement is True, then subtract the iterator value from the above-declared # resltsum. # Store it in the same variable resltsum. resltsum -= itr else: # Else if the statement is False, then add the iterator value to the above-declared # resltsum. # Store it in the same variable resltsum. resltsum += itr # Print the resltsum value which is the result of the series till the given Number N. print( "The total sum of the series till the given number {", gvn_numb, "} = ", resltsum)

**Output:**

Enter some Random Number = 7 The total sum of the series till the given number { 7 } = 4

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