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

#define getrp() ({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) ({unsigned _z=v;do*--wp=_z%10+48;while(_z/=10);})
#define wt1(v) ({char wbuf[64],*wp=wbuf+sizeof wbuf;wt(v);write(1,wp,wbuf+sizeof wbuf-wp);})
#define rep(v,e) for(int v=0;v<e;++v)
#define MD 998244353

void sort_aux(unsigned*a,unsigned*b,int n){
	int c[256];
	for(int i=0;i<256;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&255];
	}
	int t=0;
	for(int i=0;i<256;++i){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		b[c[a[i]&255]++]=a[i]>>8|a[i]<<24;
	}
}

void sort(unsigned*a,int n){
	unsigned*b=a+n;
	sort_aux(a,b,n);
	sort_aux(b,a,n);
	sort_aux(a,b,n);
	sort_aux(b,a,n);
}

unsigned a[200000*2];

int main(){
	int n;
	unsigned k;
	{
		char*rp=getrp();
		n=rd()*2;
		k=rd();
		rep(i,n){
			a[i]=rd()<<1|!(i&1);
		}
	}
	sort(a,n);
	{
		unsigned b=0,y=1,z=0;
		rep(i,n){
			unsigned x=a[i];
			if(x&1){
				z=(1ull*z*k+1ull*y*b)%MD;
				y=y*1ull*(k-b)%MD;
				++b;
			}else{
				--b;
			}
		}
		wt1(z);
	}
	_exit(0);
}