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>
int main()
{
    long a=0,b=0,c=0;
  	long j,i;
    int f;
	scanf("%d", &a);
//printf("%d", a);
//a = int(input())
c = (a-1)*2-1;
for (i = 2; i<=a; i++){
  f = 0;
  for (j = 2; j<=a; j++){
    if (f==1) continue;
    printf("ii%d\n", i);
    printf("jj%d\n", j);
    b = i*j;
    if (b >= a){
      f=1;
      continue;
    }
    c = c+1;
    //printf("ii%d\n", i);
    //printf("jj%d\n", j);
    //printf("bbbb%d\n", b);
    
  }
}
printf("%d\n", c);
    
}