Thread: How to arrange the input/output order?

Hello,
for our school project, we have to make a program which involves three students and the prices each of them paid for the meals. The program has to calculate how much each of the students has to pay/receive to/from the others.
Most of it, we got from our teacher. The error we are getting is that we have to 'take care of the input/output order'. So if you type in the names/numbers of the students in a different way, so for example if you type first number 1, then 0, then 2 and 0 and 1 have to pay money to number 2, number 0 has to be in front of 1. Our output is that number 1 is in front of number 0.
insert

Code:

 
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>

/* type definition of student */
typedef struct student {
  int who;     /* 0=John, 1=Peter, 2=William */
  float paid;  /* amount that student paid   */
} student;

/* global variables */
student firstStudent, secondStudent, thirdStudent;

/************************************************************************
 * ABSTRACT DATA TYPE: the following functions form the ADT student.
 * Do not change the ADT part of this program !
 */

/* read the info of a student from the keyboard and return it. */
void readStudent(student *stud) {
  scanf("%d %f", &stud->who, &stud->paid);
}

/* print the name of a student. */
void printNameOfStudent(student stud) {
  printf("%s", (stud.who == 0 ? "John" : (stud.who == 1 ? "Peter" : "William")));
}

/* returns the amount that a student paid. */
float paidByStudent(student stud) {
  return stud.paid;
}

/* swaps two students */
void swapStudents(student *a, student *b) {
  student h = *a;
  *a = *b;
  *b = h;
}

/************************************************************************/


/* remainder of the program in which the ADT student is used. */

/*
 * Reads the entire input from the keyboard and stores 
 * it in the appropriate global variables.
 */
void readInput() {
  readStudent(&firstStudent);
  readStudent(&secondStudent);
  readStudent(&thirdStudent);
}


int main(int argc, char *argv[]) {
  readInput();
  
float average, difference;
   readInput();
 
    average = ((paidByStudent(firstStudent) + paidByStudent(secondStudent) + paidByStudent(thirdStudent)) / 3);
        
/*ordering*/
        if (paidByStudent(thirdStudent) - average == paidByStudent(firstStudent) - average) {
            swapStudents(&thirdStudent, &firstStudent);
        } else {
            if (paidByStudent(thirdStudent) - average < paidByStudent(firstStudent) - average) {
            swapStudents(&thirdStudent, &firstStudent);
            }
        }
        
        if (paidByStudent(secondStudent) - average == paidByStudent(firstStudent) - average) {
            swapStudents(&secondStudent, &firstStudent);
        } else {
            if (paidByStudent(secondStudent) - average < paidByStudent(firstStudent) - average) {
            swapStudents(&secondStudent, &firstStudent);
            }
        }
        
        if (paidByStudent(secondStudent) - average == paidByStudent(thirdStudent) - average) {
        } else {
            if (paidByStudent(secondStudent) - average > paidByStudent(thirdStudent) - average) {
            swapStudents(&secondStudent, &thirdStudent);
            }
        }
       
        /* ordering when outcome is the same */
        /*         if (paidByStudent(thirdStudent) - average == paidByStudent(firstStudent) - average){
            swapStudents(&thirdStudent, &firstStudent);
        } else { */
        

    
       
/* printing */
        printNameOfStudent(firstStudent);
        if (paidByStudent(firstStudent) < average){
        difference = average - paidByStudent(firstStudent);
        printf(" pays %3.2f\n", difference);
        } else {           
                difference = ((average - paidByStudent(firstStudent)) *-1);
                printf(" receives %3.2f\n", difference);
        }
    
        printNameOfStudent(secondStudent);
        if (paidByStudent(secondStudent) > average){
        difference = ((average - paidByStudent(secondStudent)) *-1);
        printf(" receives %3.2f\n", difference);
        } else {    
            difference = average - paidByStudent(secondStudent);
            printf(" pays %3.2f\n", difference);
        }
            
        printNameOfStudent(thirdStudent);
        if (paidByStudent(thirdStudent) < average){
        difference = average - paidByStudent(thirdStudent);
        printf(" pays %3.2f\n", difference);
        } else {      
            difference = ((average - paidByStudent(thirdStudent)) *-1 );
            printf(" receives %3.2f\n", difference);
        }
    return 0;
}

Do you have any ideas on how to solve this?