x+y#11796
Given an integer (1 \leq r \leq 10^5).
You need to find the number of pairs of integers that satisfy the following conditions:
0 \le x < y \le r;
x+y=r.
A single line contains the number (1 \le r \le 10^5).
Output a single number — the number of pairs that satisfy the condition.
Example 1
Example 2
For r = 5 the suitable pairs are: , , .