diff --git a/6th.cpp b/6th.cpp
new file mode 100644
index 0000000..ce9b70e
--- /dev/null
+++ b/6th.cpp
@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define MAX_STUDENTS 100
+typedef struct {
+	int ID;
+	char name[30];
+	int classnumber;
+	float score1,score2,score3;
+}student;
+
+int find(int ID,const char *name,student students[],int count){
+	int i;
+	for(i=0;i<count;i++){
+		if(students[i].ID==ID){
+			return i;
+		}
+	}
+	return -1;
+}
+void modifystudent(student students[],int index,float newscore1,float newscore2,float newscore3){
+	students[index].score1=newscore1;
+	students[index].score2=newscore2;
+	students[index].score3=newscore3;
+}
+
+
+int compare(const void*a,const void *b){
+	student s1=*(student*)a;
+	student s2=*(student*)b;
+	if(s1.classnumber!=s2.classnumber){
+		return s1.classnumber-s2.classnumber;
+	}
+	float total1=s1.score1+s1.score2+s1.score3;
+	float total2=s2.score1+s2.score2+s2.score3;
+	return total2-total1;
+}
+void print(student students[],int n,int modifiedindex){
+	int classn=-1;
+	
+	int j;
+	for(j=0;j<n;j++){
+		if(students[j].classnumber!=classn){
+			classn=students[j].classnumber;
+			
+			printf("%d %d %s %.1f %.1f %.1f",students[j].classnumber,students[j].ID,students[j].name,students[j].score1,students[j].score2,students[j].score3);
+				if(j==modifiedindex){
+			printf(" modified\n");
+		}
+		}else{
+		printf("   %d %s %.1f %.1f %.1f\n",students[j].ID,students[j].name,students[j].score1,students[j].score2,students[j].score3);
+	    	}
+	
+		
+	}
+}
+int main(){
+	student students[MAX_STUDENTS];
+    int n = 3;
+    students[0].ID= 10001;
+    students[0].classnumber = 11;
+    strcpy(students[0].name, "Zhang");
+    students[0].score1 = 99.5;
+    students[0].score2 = 88.5;
+    students[0].score3 = 89.5;
+
+    students[1].ID= 10002;
+    students[1].classnumber = 12;
+    strcpy(students[1].name, "Yang");
+    students[1].score1 = 77.9;
+    students[1].score2 = 56.5;
+    students[1].score3 = 87.5;
+
+    students[2].ID= 10003;
+    students[2].classnumber= 11;
+    strcpy(students[2].name, "Liang");
+    students[2].score1 = 92.5;
+    students[2].score2 = 99.0;
+    students[2].score3 = 60.5;
+    qsort(students,n,sizeof(student),compare);
+    student newstudent;
+    scanf("%d %d %s %f %f %f",&newstudent.ID,&newstudent.classnumber,&newstudent.name,&newstudent.score1,&newstudent.score2,&newstudent.score3);
+	int index=find(newstudent.ID,NULL,students,n);
+	int modifiedindex=-1;
+	if(index!=-1){
+		modifystudent(students,index,newstudent.score1,newstudent.score2,newstudent.score3);
+		modifiedindex=index;
+	}
+	
+	print(students,n, modifiedindex);
+	return 0;
+}
+
+
+
+
+
+
+