- To print sum of 1 to N

User Input: 10

Output:

Sum of 1 to 10 : 55

```
n=int(input("Enter last number :"))
print("sum of 1 to ",n," : ", int((n*(n+1))/2))
```

Enter last number : 10 Sum of 1 to 10 : 55Program

number

We are using the formula of sum of natural numbers (1 to N)

`(N*(N+1))/2 // N is the last number`

Concept