diff --git a/5.c b/5.c
new file mode 100644
index 0000000..e2b1a4e
--- /dev/null
+++ b/5.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <string.h>
+
+struct Data
+{
+	int ID;
+	int Class;
+	float score1;
+	float score2;
+	float score3;
+	char name[101];
+} stu[1001];
+int stl = 0;
+struct Data* stuflag = 0;
+
+float total(struct Data* a) {
+	return a->score1 + a->score2 + a->score3;
+}
+
+void swap(struct Data* a, struct Data* b) {
+	struct Data t = *a;
+	*a = *b;
+	*b = t;
+
+	if (a == stuflag) stuflag = b;
+else 
+	if (b == stuflag) stuflag = a;
+}
+
+void Sort() {
+	int i, j;
+	for(i = 0; i < stl-1; i++) {
+		for (j = 0; j < stl-i-1; j++) {
+			if (stu[j].Class < stu[j+1].Class) continue;
+			if (stu[j].Class > stu[j+1].Class || 
+			total(&stu[j]) < total(&stu[j+1])) swap(&stu[j], &stu[j+1]);
+		}
+	}
+}
+
+void input1() {
+	scanf("%d", &stu[stl].ID);
+	scanf("%f", &stu[stl].score1);
+	scanf("%f", &stu[stl].score2);
+	scanf("%f", &stu[stl].score3);
+	stl++;
+}
+
+
+void Input() {
+	printf("Please input info of three students:\n");
+	input1();input1();input1();
+	if (total(&stu[stl-3]) < total(&stu[stl-2])) swap(&stu[stl-3], &stu[stl-2]);
+	if (total(&stu[stl-2]) < total(&stu[stl-1])) swap(&stu[stl-2], &stu[stl-1]);
+	if (total(&stu[stl-3]) < total(&stu[stl-2])) swap(&stu[stl-3], &stu[stl-2]);
+	printf("%d,%.1f,%.1f\n", stu[stl-3].ID, total(&stu[stl-3]), total(&stu[stl-3])/3.0f);
+	printf("%d,%.1f,%.1f\n", stu[stl-2].ID, total(&stu[stl-2]), total(&stu[stl-2])/3.0f);
+	printf("%d,%.1f,%.1f\n", stu[stl-1].ID, total(&stu[stl-1]), total(&stu[stl-1])/3.0f);
+}
+
+void print1(struct Data* a) {
+	printf("%d %d %s %2.1f %2.1f %2.1f", a->ID, a->Class, a->name, 
+					a->score1, a->score2, a->score3);
+	if (a == stuflag) printf(" inserted");
+	printf("\n");
+}
+
+void Remove(struct Data* r) {
+	for(; r+1 < stu+stl; r++) {
+		*r = *(r+1);
+	}
+	stl--;
+}
+
+void Delete() {
+	stu[0] = (struct Data){10001, 11, 99.5, 88.5, 89.5, "Zhang"};
+	stu[1] = (struct Data){10002, 12, 77.9, 56.5, 87.5, "Yang"};
+	stu[2] = (struct Data){10003, 11, 92.5, 89.0, 60.5, "Liang"};
+	stl = 3;
+	
+	int ID = -1; char name[101];
+	scanf("%s", name);
+	getchar();
+	int NumFlag = 1, i;
+	for(i = 0; name[i]!='\0'; i++)
+		if (name[i] < '0' || name[i] > '9') {
+			NumFlag = 0; break;
+		}
+	if (NumFlag) {
+		sscanf(name, "%d", &ID);
+		name[0] = '\0';
+	}
+	
+	printf("Are you sure(yes/no)?\n");
+	char t;
+	scanf("%c", &t);
+	if (t == 'y') {
+		for(i=0; i<stl; i++) {
+			if(stu[i].ID == ID || name[0]!='\0' && strcmp(stu[i].name, name) == 0) {
+				Remove(stu + i);
+				break;
+			}
+		}
+	}
+	for (i=0; i<stl; i++) {
+		print1(stu + i);
+	}
+}
+
+int main() {
+	Delete();
+}
\ No newline at end of file