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小艾给小兰出了一道题：一个 $n\times n$ 的方格，每个格子放一个 $1\sim c$ 的整数，有多少种方案使得任何一行有至少两种数出现，任何一列至少有两种数出现？
刚学过数数的小兰随便推了推，就解决了这个问题。
于是小艾加大了难度：如果 $i=j$ 这条对角线上的数都必须是 $1$，又有多少种方案？
请你帮小兰算一算，答案对 $998244353$ 取模。
一行输入两个正整数 $n,c$，如题意所示。
输出一个数，表示方案数对 $998244353$ 取模的结果。
2 3
4
3 3
416
5 2
592260
对于 $100\%$ 的数据，保证 $2\le n\le 10^6, 2\le c\le 10^8$。
| 数据点 | $1,2$ | $3$ | $4$ | $5$ | $6$ | $7$ | $8$ | $9$ | $10$ |
|---|---|---|---|---|---|---|---|---|---|
| $n=$ | $2$ | $5$ | $50$ | $200$ | $500$ | $2000$ | $5000$ | $10^5$ | $10^6$ |
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