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(void){
    int N,n,count=0,insu=1,num;

    scanf("%d",&N);
    int a[N];
    for(int n=0;n<N;n++)a[n]=0;

    for(n=1;n<N;n++){
        num=n;

    for(int j=2;j<=n;j++){
        //if(n%j==0)insu++;
        //printf("doko");

        int j=2;
        while(num%j==0){
            a[j]++;
            num/=j;
        }
   }
    for (int i = 2; i <= n; i++)
	{	
		insu*=a[i]+1;
	}
    for(int n=0;n<N;n++)a[n]=0;
        //if(insu==1)insu=0;
        count+=insu;
        insu=1;
    }

    printf("%d",count);
    return 0;
}