diff --git a/Admin.h b/Admin.h
index 5baf4cb..6ffe518 100644
--- a/Admin.h
+++ b/Admin.h
@@ -36,7 +36,7 @@ public:
 				ss.str(username);
 				int id;
 				ss >> id;
-				for (int i = 0; i < db_st_list.size; i++) {
+				for (size_t i = 0; i < db_st_list.size; i++) {
 					if (db_st_list.list[i].st_number == id) {
 						db_st_list.removeFromList(i);
 						return 1;
@@ -44,7 +44,7 @@ public:
 				}
 			}
 			else {
-				for (int i = 0; i < db_tc_list.size; i++) {
+				for (size_t i = 0; i < db_tc_list.size; i++) {
 					if (db_tc_list.list[i].tc_identify == username) {
 						db_tc_list.removeFromList(i);
 						return 1;
diff --git a/Process.cpp b/Process.cpp
index 2c958de..5cc9dfb 100644
--- a/Process.cpp
+++ b/Process.cpp
@@ -476,7 +476,7 @@ bool teacherProcess(Teacher& tc, UserList& user_list, StudentCourseList& db_st_c
 
 #pragma region Tien
 void to_upper(string &s) {
-	for (int i = 0; i < s.length(); i++) {
+	for (size_t i = 0; i < s.length(); i++) {
 		s[i] = toupper(s[i]);
 	}
 }
@@ -562,7 +562,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 	else if (agvList.list[0] == "ss") {
 		if (agvList.size > 1) {
 			agvList.removeFromList(0);
-			for (int i = 0; i < agvList.size; i++) {
+			for (size_t i = 0; i < agvList.size; i++) {
 				to_upper(agvList.list[i]);
 			}
 			StudentList sList = db_st_list.findStudentByNameKeyWord(agvList.list, agvList.size);
@@ -606,7 +606,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 	else if (agvList.list[0] == "st") {
 		if (agvList.size > 1) {
 			agvList.removeFromList(0);
-			for (int i = 0; i < agvList.size; i++) {
+			for (size_t i = 0; i < agvList.size; i++) {
 				to_upper(agvList.list[i]);
 			}
 			TeacherList tList = db_tc_list.findTeacherByNameKeyword(agvList.list, agvList.size);
@@ -664,7 +664,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 				else removeList.addToList(username);
 			} while (true);
 			arrayList<string> remove_unsuccess;
-			for (int i = 1; i < removeList.size; i++) {
+			for (size_t i = 1; i < removeList.size; i++) {
 				if (ad.removeUser(removeList.list[i], user_list, db_st_list, db_tc_list) == 1) {
 
 				}
@@ -677,7 +677,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 			}
 			else {
 				cout << "Some user remove unsuccessful! That is:" << endl;
-				for (int j = 0; j < remove_unsuccess.size; j++) {
+				for (size_t j = 0; j < remove_unsuccess.size; j++) {
 					cout << j + 1 << ".\t" << remove_unsuccess.list[j] << endl;
 				}
 				cout << "Other user remove successful!" << endl;
@@ -687,7 +687,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 		else
 		{
 			arrayList<string> remove_unsuccess;
-			for (int i = 1; i < agvList.size; i++) {
+			for (size_t i = 1; i < agvList.size; i++) {
 				if (ad.removeUser(agvList.list[i], user_list, db_st_list, db_tc_list) == 1) {
 					
 				}
@@ -700,7 +700,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 			}
 			else {
 				cout << "Some user remove unsuccessful! That is:" << endl;
-				for (int j = 0; j < remove_unsuccess.size; j++) {
+				for (size_t j = 0; j < remove_unsuccess.size; j++) {
 					cout << j + 1 << ".\t" << remove_unsuccess.list[j] << endl;
 				}
 				cout << "Other user remove successful!" << endl;
@@ -723,7 +723,7 @@ bool adminProcess(Admin& ad, UserList& user_list, StudentList& db_st_list, Teach
 			cout << setw(40) << setfill(' ') << left << "Add Student" << "[as]" << endl;
 			cout << "Input <as> then input student's informations." << endl << endl;
 			cout << setw(40) << setfill(' ') << left << "Remove User" << "[ru]" << endl;
-			cout << "Input <ru> then input list of usernames. Or input <ru> <list of username you want to remove (separate by space)." << endl << endl;
+			cout << "Input <ru> then input list of usernames. Or input <ru> <list of username you want to remove (separate by space)>." << endl << endl;
 			cout << setw(40) << setfill(' ') << left << "Search Teacher by name" << "[st]" << endl;
 			cout << "Input <st> <list of teachers' name> to search. Or input <st> then input <name>." << endl;
 			cout << "Input as this format <identify, name, birthday, \"phone number\", \"hometown\"> (separate by comma):" << endl << endl;
diff --git a/user.csv b/user.csv
index 28c16c4..d3cfdc7 100644
--- a/user.csv
+++ b/user.csv
@@ -78,4 +78,4 @@ S0997,S0997,teacher
 S0998,S0998,teacher
 S0999,S0999,teacher
 S1000,S1000,teacher
-admin,a,admin
\ No newline at end of file
+admin,a,admin