c언어 정렬이랑 if - else문좀 봐주시면감사하겠습니다.

#include <stdio.h>
 
#define Max_person 4
 
struct person
{
	char name[20];
	int kor, eng, math, total, num;
	double avg;
};
 
int main(void)
{
	struct person per[Max_person];
	struct person *p=per;
	int i;
 
	for(i=0; i<Max_person; i++)
	{
		printf("학번을 입력하세요 : ");
		scanf("%d", &p->num);
		printf("이름을 입력하세요 : ");
		scanf("%s", p->name);
		printf("국어점수 : ");
		scanf("%d", &p->kor);
		printf("영어점수 : ");
		scanf("%d", &p->eng);
		printf("수학점수 : ");
		scanf("%d", &p->math);
		p->total=p->kor + p->eng + p->math;
		p->avg=p->total/3.0;
		p++;
	}
	printf("***************************************************************\n");
	printf("\t번호\t이름\t국어\t영어\t수학\t총점\t평균\n");
	printf("***************************************************************\n");
	p=per;
	for(i=0; i<Max_person; i++)
	{
		printf("%3d\t%5s\t%3d\t%3d\t%3d\t%3d\t%3.2f\n", p->num, p->name, p->kor, p->eng, p->math, p->total, p->avg);
		p++;
	}
	printf("***************************************************************\n");
 
	return 0;
 
}