#D10987. A x B + C
A x B + C
A x B + C
Given is a positive integer N. How many tuples (A,B,C) of positive integers satisfy A \times B + C = N?
Constraints
- 2 \leq N \leq 10^6
- All values in input are integers.
Input
Input is given from Standard Input in the following format:
N
Output
Print the answer.
Examples
Input
3
Output
3
Input
100
Output
473
Input
1000000
Output
13969985
inputFormat
input are integers.
Input
Input is given from Standard Input in the following format:
N
outputFormat
Output
Print the answer.
Examples
Input
3
Output
3
Input
100
Output
473
Input
1000000
Output
13969985
样例
33