Problem:
Score : 300 points

Problem Statement

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.

Sample Input 1

3

Sample Output 1

3

There are 3 tuples of integers that satisfy A \times B + C = 3: (A, B, C) = (1, 1, 2), (1, 2, 1), (2, 1, 1).

Sample Input 2

100

Sample Output 2

473

Sample Input 3

1000000

Sample Output 3

13969985

Solution in C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <math.h>
int main(void){
  long long int n,x,kari,p;
  p=1; kari=0;
  long long int yak=0;
  scanf("%lld",&n);

  for(int i=1;i<n;i++){
    x=n-i;
    for(int j=1;j<=x;++j){
      if(x%j==0){            //約数
        yak++;
      }
    }

    for(int l=1;l<=yak;++l){
      p=p*l;                     //p通り
    }

  kari=kari+p;
  yak=0;

  }

  printf("%lld",kari);
 return 0;
}