如何用二维数组打印26×26个英文字母

后面行的字母并不是按顺序，应该怎么实现该语句呢？
定义了一个26乘26的字符数组，写出为它赋如下值的语句

#include <stdio.h>
int main() {
    char a[26][26];
    int x,y;

    for (y=0;y<26;y++) {
        for (x=0;x<26;x++) {
            a[y][x]='a'+(x+y)%26;
        }
    }

    for (y=0;y<26;y++) {
        printf("%.26s\n",a[y]);
    }

    return 0;
}
//abcdefghijklmnopqrstuvwxyz
//bcdefghijklmnopqrstuvwxyza
//cdefghijklmnopqrstuvwxyzab
//defghijklmnopqrstuvwxyzabc
//efghijklmnopqrstuvwxyzabcd
//fghijklmnopqrstuvwxyzabcde
//ghijklmnopqrstuvwxyzabcdef
//hijklmnopqrstuvwxyzabcdefg
//ijklmnopqrstuvwxyzabcdefgh
//jklmnopqrstuvwxyzabcdefghi
//klmnopqrstuvwxyzabcdefghij
//lmnopqrstuvwxyzabcdefghijk
//mnopqrstuvwxyzabcdefghijkl
//nopqrstuvwxyzabcdefghijklm
//opqrstuvwxyzabcdefghijklmn
//pqrstuvwxyzabcdefghijklmno
//qrstuvwxyzabcdefghijklmnop
//rstuvwxyzabcdefghijklmnopq
//stuvwxyzabcdefghijklmnopqr
//tuvwxyzabcdefghijklmnopqrs
//uvwxyzabcdefghijklmnopqrst
//vwxyzabcdefghijklmnopqrstu
//wxyzabcdefghijklmnopqrstuv
//xyzabcdefghijklmnopqrstuvw
//yzabcdefghijklmnopqrstuvwx
//zabcdefghijklmnopqrstuvwxy
//