makin a grading system in c

 #include<stdio.h>

int main()

{

int num;

printf("Enter the number of the student:\n");

scanf("%d", &num);

if(num>=91 && num<=100)

printf("Grade O: Outstanding");

else if(num>=81 && num<=90)

printf("Grade E: Excelent");

        else if(num>=71 && num<=80)

printf("Grade A: Very Good");

else if(num>=61 && num<=70)

printf("Grade B: Good");

else if(num>=51 && num<=60)

printf("Grade C: Saisfactory");

else if(num>=41 && num<=50)

printf("Grade D: Standard");

else

printf("Grade F: Fail");

return 0;

    

}