Write a program which reads a positive integer value N, calculates and shows the sum of the even numbers < = N.

Difficulty level
This exercise is mostly suitable for students 
#include<stdio.h>
int main()
{
	int N, i, sum;
	
	sum=0;
	
	do{
	    printf("Enter N: ");
	    scanf("%d",&N);
	}while(N<0);
	
	
	for(i=1;i<=N; i++)
	    if(i%2==0)
	        sum+=i;
	        
    printf("Sum of the even numbers <= %d is equal to %d\n",N, sum);
	return 0;
}
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