注意点：
这题不能用gets（会把空格吃掉）；

#include<cstdio>
#include<cstring>

void reverse(char s[]){
    int len = strlen(s);
    for(int i=0;i<len/2;i++){
        char temp = s[i];
        s[i] = s[len-i-1];
        s[len-i-1] = temp; 
    }
}

int main(){

    char A[110],B[110],ans[110]={0};

    scanf("%s %s",A,B);

    reverse(A);
    reverse(B);

    int lenA = strlen(A);
    int lenB = strlen(B);

    int len = lenA > lenB ? lenA:lenB;

    for(int i=0;i<len;i++){
        int numA = i<lenA? A[i]-'0':0;
        int numB = i<lenB? B[i]-'0':0;        //这里再次把字符转换为数字，并且位数较少的那个数，补0 

        if(i%2==0){        //偶数的情况
            int temp = numA+numB;
            temp = temp%13;
            if(temp==10)    ans[i] = 'J';
            else if(temp==11)    ans[i] = 'Q';
            else if(temp==12)    ans[i] = 'K';
            else
                ans[i] = temp+'0';    
        }else{
            int temp = numB-numA;
            if(temp<0)    temp+=10;
            ans[i] = temp+'0';
        }

    }

    reverse(ans);

    puts(ans);


    return 0;
}