How to add limits on inputs of multiple integer?

I want to add a limit on all variables >=40 and <=100. if the inputs matches with both condition then program will execute otherwise it will show invalid.. how will I do it?

#include<stdio.h>
  int main()
 {
    int s1, s2, s3, s4, s5, avg;
    printf("\n Enter your Subject Numbers:");
    scanf("%d%d%d%d%d", &s1, &s2, &s3, &s4, &s5);

avg = (s1+s2+s3+s4+s5)/5;
if (avg>=80)
{
    printf("\n Your Grade is : A+");
}
else if (avg>=70)
{
    printf("\n Your Grade is : A ");
}
else if (avg>=60)
{   
    printf("\n Your Grade is : A- ");
}
else if (avg>=50)
{
    printf("\n Your Grade is : B ");
}
else if (avg>=40)
{
    printf("\n Your Grade is : C ");
}
else if (avg<40)
{
    printf("\n Your Grade is : F ");
}
return 0;

}