#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();

#define rd(v) long v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define wt(v) {long _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rep(v,e) for(long v=0;v<e;++v)
#define rep3(v,s,e) for(long v=s;v<e;++v)

#define MD 998244353

int inverse(int a){
	int b=MD;
	int u=1;
	int v=0;
	int s,t;
	while(b){
		t=a/b;
		s=b; b=a-t*b; a=s;
		s=v; v=u-t*v; u=s;
	}
	if(u<0){
		u+=MD;
	}
	return u;
}

#define FAC_N 200001
int fac[FAC_N];

void mkfac(){
	long f=1;
	fac[0]=f;
	rep3(i,1,FAC_N){
		fac[i]=f=f*i%MD;
	}
}

main(){
	mkfac();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rd(m);
	long a=0;
	long z=0;
	long v=inverse(fac[n]);
	rep(j,n){
		if(a<=j) {
			rd(ai);
			a=ai;
		}
		z=(z+v*fac[n-j-1]%MD*a)%MD;
		v=v*(n-j)%MD;
	}

	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}