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: Time Limit Exceeded)

#include <stdio.h>


int main(void){
    // 自分の得意な言語で
    // Let's チャレンジ！！

    long int n,x;
    //long int a[10000];
     int count=0;
   

    scanf("%ld",&n);
    x=n;

  for(int j=1;j<n;j++){
    x=n-j;
    for(int i=1; i<=x; ++i ){
    if( x%i == 0 )
    //a[count]=i;
    count++;
     // printf("%d ", i);
    }
    
  }


    

      
      printf("%d\n",count);
   


   
    
    return 0;
}