โปรแกรมคำนวณเกรด

#include<stdio.h>
 main(){
 int x=0;
 printf("Program by Warunchai Lohitsiri M.5-11 No.2\n");
 printf("// Input Score : ");
 scanf("%d",&x);
 printf("\n");
 while(x>100){
 printf("\nInput must < 100\n// Input Score : ");
 scanf("%d",&x);

printf("\n");
 }
 if(x>=80)
 printf("Grade A");
 else if(x>=70)
 printf("Grade B");
 else if(x>=60)
 printf("Grade C");
 else if(x>=50)
 printf("Grade D");
 else
 printf("Grade 0");
 getch();
 }