Maximum Cost Exchange

//Please review my code
#include <stdio.h>
#include <math.h>
main()
{
    int students, i = 0;
    float average, total = 0.0, sum = 0.0, num;
    float *costs;
    prinf("Enter the number of students: ");
    scanf("%d\n",students);
    while(students != 0){
        costs = malloc(students*sizeof(double));
        while(i < students){
            scanf("%f",&num);
            sum += num;
            costs[i++] = num;
        } average = sum/students;
        for(i = 0; i < students; i++){
            total += floor((costs[i] - average)*100)/100;
        } printf("%f",total);
        i = 0;
        sum = 0.0;
        total = 0.0;
        free(costs);
        prinf("Enter the number of students: ");
        scanf("%d\n",students);
    }
}