程序代码：

#include<stdio.h>
int main()
{
    int a,b;
    scanf("%c %c",&a,&b);
    if('a'<=a&&a<='z'&&'a'<=b&&b<='z')
        if(a>b)
            printf("%c\n",a);
        else printf("%c\n",b);
    if('A'<=a&&a<='Z'&&'A'<=b&&b<='Z')
        if(a>b)
            printf("%c\n",a);
        else printf("%c\n",b);
    if('a'<=a&&a<='z'&&'A'<=b&&b<='Z')
        printf("%c\n",b);
    if('a'<=b&&b<='z'&&'A'<=a&&a<='Z')
        printf("%c\n",a);
}