#include <stdio.h>
#include <string.h>
struct student{
 char name[20];
 int id;
 char sex;
 int kor, eng, math;
};

void main(){
 struct student std[5];
 int a, i;
 int max1 = std[0].kor;
 int max2 = std[0].eng;
 int max3 = std[0].math;
 int save1 = 0, save2 = 0, save3 = 0;
 while (1){
  printf("1.load 2.show 3.best score 4.male students 5.female students 6.change\nselect menu");
  scanf("%d", &a);
  switch (a){
  case 1:
   printf("enter name, id, sex, kor, eng, math for 5 students\n");
   for (i = 0; i < 5; i++){
    printf("student %d", i + 1);
    scanf("%s %d %c %d %d %d", &std[i].name, &std[i].id, &std[i].sex, std[i].kor, &std[i].eng, &std[i].math);
   }
   break;
  case 2:
   printf("now displaying the students\n");
   for (i = 0; i < 5; i++){
    printf("student %d\n", i);
    printf("name:%s student ID:%d sex:%c\n", std[i].name, std[i].id, std[i].sex);
    printf("kor score:%d  eng score:%d math score:%d\n", std[i].kor, std[i].eng, std[i].math);
   }
   break;
  case 3:
   for (i = 0; i < 5; i++){
    if (max1 < std[i].kor){
     max1 = std[i].kor;
     i = save1;
    }
   }
   for (i = 0; i < 5; i++){
    if (max2 < std[i].eng){
     max2 = std[i].eng;
     i = save2;
    }
    for (i = 0; i < 5; i++){
     if (max3 < std[i].math){
      max3 = std[i].math;
      i = save3;
     }
    }
    printf("best score for korean : %s %d", std[save1].name, max1);
    printf("best score for korean : %s %d", std[save2].name, max2);
    printf("best score for korean : %s %d", std[save3].name, max3);
    break;
  case 4:
   for (i = 0; i < 5; i++){
    if (std[i].sex = 'M')
     for (i = 0; i < 5; i++){
      printf("student %d", i + 1);
      scanf("%s %d %c %d %d %d", &std[i].name, &std[i].id, &std[i].sex, std[i].kor, &std[i].eng, &std[i].math);
     }
   }
  case 5:
   for (i = 0; i < 5; i++){
    if (std[i].sex = 'F')
     for (i = 0; i < 5; i++){
      printf("student %d", i + 1);
      scanf("%s %d %c %d %d %d", &std[i].name, &std[i].id, &std[i].sex, std[i].kor, &std[i].eng, &std[i].math);
     }
   }
  case 6:
   int j = 0;
   printf("enter student ID");
   scanf("%d", &j);
   for (i = 0; i < 5; i++)
    if (std[i].id = j){
     printf("enter new data");
     scanf("%s %d %c %d %d %d", &std[i].name, &std[i].id, &std[i].sex, std[i].kor, &std[i].eng, &std[i].math);
    }
   }
  }
 }
}

실행은 되는데 student1 입력하면 student2입력하도록 나와야 되는데 student1 입력하면 오류나요ㅠㅠㅠㅠㅠ