11-26.c

#include <stdio.h>
int main()
{
    int a;
    printf("please input grade:");
    scanf_s("%d", &a);
    switch (a / 10)
    {
    case 10:
    case 9:
        printf("A\n");
        break;
    case 8:
        printf("B\n");
        break;
    case 7:
        printf("C\n");
        break;
    case 6:
        printf("D\n");
        break;
    case 5:
    case 4:
    case 3:
    case 2:
    case 1:
    case 0:
        printf("E\n");
        break;
    default:
        printf("error\n");
    }
    system("pause");
    return 0;
}