You are given a number NN. Find the sum of all numbers from 11 to NN.
Input:
- First-line will contain the number NN.
Output:
Print the answer in a single line.
Constraints
- 1≤N≤1091≤N≤109
Sample Input 1:
4
Sample Output 1:
10
n=int(input())
abil=int((n*(n+1))/2)
print(abil)