[C++]if..then..else กับการหาเกรด

//Program by Kumpho
#include <stdio.h>
#include "conio.h"
#include "stdlib.h"

main()
{
   int score;
   float gr;
   char bye;
       /* Generate Grede
        0-49 =0
       50-54=1
       55-59=1.5
       60-64=2
       65-69=2.5
       70-74=3
       75-79=3.5
       80-100=4
          */
do
  {
          printf("Program IF..THEN_ELSE to check Grade. \n============================\n");
          printf("Enter your score[0-100]? :");    
          scanf("%d",&score);
       if (score<50) gr=0;
       else if (score<55) gr=1;
       else if (score<60) gr=1.5;
       else if (score<65) gr=2;
       else if (score<70) gr=2.5;
       else if (score<75) gr=3;
       else if (score<80) gr=3.5;
       else if (score<=100) gr=4;
       else printf("Worng score!!!\n");
       printf("Grade = %.2f\n",gr);
       printf("\nDo you want to exit?[y]:");
       bye=getch();
       system("cls");
}while (bye!='y');
 
}