diff --git a/b4.c b/b4.c
new file mode 100644
index 0000000..f17820c
--- /dev/null
+++ b/b4.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+ struct Student {
+    int id;        
+    int classNum;   
+    float score1;   
+    float score2;   
+    float score3;   
+} Student;
+
+int compareStudents( struct Student studentA,  struct Student studentB)
+    {
+    if (studentA.classNum < studentB.classNum) {
+        return -1;
+    } else if (studentA.classNum > studentB.classNum) {
+        return 1;
+    } else {
+        float totalScoreA = studentA.score1 + studentA.score2 + studentA.score3;
+        float totalScoreB = studentB.score1 + studentB.score2 + studentB.score3;
+        if (totalScoreA > totalScoreB) {
+            return -1;
+        } else if (totalScoreA < totalScoreB) {
+            return 1;
+        } else {
+            return 0;
+        }
+    }
+}
+
+int main() {
+    struct Student students[4];
+    students[0].id = 10001;
+    students[0].classNum = 11;
+    students[0].score1 = 99.5;
+    students[0].score2 = 88.5;
+    students[0].score3 = 89.5;
+
+    students[1].id = 10002;
+    students[1].classNum = 12;
+    students[1].score1 = 77.9;
+    students[1].score2 = 56.5;
+    students[1].score3 = 87.5;
+
+    students[2].id = 10003;
+    students[2].classNum = 11;
+    students[2].score1 = 92.5;
+    students[2].score2 = 99.0;
+    students[2].score3 = 60.5;
+
+     struct Student newStudent;
+    
+    scanf("%d %d %f %f %f", &newStudent.id, &newStudent.classNum, &newStudent.score1, &newStudent.score2, &newStudent.score3);
+
+    int isExist = 0;
+    int i;
+    for (i = 0; i < 3; i++) {
+        if (newStudent.id == students[i].id) {
+            isExist = 1;
+            break;
+        }
+    }
+    if (isExist) {
+        printf("id had exsited");
+        printf("%d %d %.1f %.1f %.1f\n", students[0].id, students[0].classNum, students[0].score1, students[0].score2, students[0].score3);
+        return 0;
+    }
+
+    students[3] = newStudent;
+    qsort(students, 4, sizeof(Student), compareStudents);
+
+    for (i = 0; i < 4; i++) {
+        printf("%d %d %.1f %.1f %.1f", students[i].id, students[i].classNum, students[i].score1, students[i].score2, students[i].score3);
+        if (students[i].id == newStudent.id) {
+            printf(" inserted\n");
+        } else {
+            printf("\n");
+        }
+    }
+
+    return 0;
+}