#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
namespace my{
using ml=atcoder::modint998244353;
auto&operator>>(istream&i,ml&x){int t;i>>t;x=t;return i;}
auto&operator<<(ostream&o,const ml&x){return o<<(int)x.val();}
#define eb emplace_back
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define VV(n,...) vec<ll>__VA_ARGS__;setsize({n},__VA_ARGS__);vin(__VA_ARGS__)
#define FO(n) for(ll ij=n;ij--;)
#define FOR(i,...) for(auto[i,i##stop,i##step]=range(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define fo(i,...) FO##__VA_OPT__(R)(i __VA_OPT__(,__VA_ARGS__))
#define of(i,...) for(auto[i,i##stop,i##step]=range(1,__VA_ARGS__);i>=i##stop;i-=i##step)
#define fe(a,i,...) for(auto&&__VA_OPT__([)i __VA_OPT__(,__VA_ARGS__]):a)
#define single_testcase void solve();}int main(){my::io();my::solve();}namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
template<class...A>constexpr auto range(bool s,A...a){array<ll,3>r{0,0,1};ll I=0;((r[I++]=a),...);if(!s&&I==1)swap(r[0],r[1]);r[0]-=s;return r;}
constexpr char nl=10;
constexpr char sp=32;
ll pwm1(ll n){return 1-2*(n&1);}

template<class F=less<>>auto&sort(auto&a,const F&f={}){ranges::sort(a,f);return a;}
auto&unique(auto&a){sort(a).erase(ranges::unique(a).begin(),a.end());return a;}

template<class V>concept vectorial=is_base_of_v<vector<typename V::value_type>,V>;
template<class T>struct vec_attr{using core_type=T;static constexpr int d=0;};
template<vectorial V>struct vec_attr<V>{using core_type=typename vec_attr<typename V::value_type>::core_type;static constexpr int d=vec_attr<typename V::value_type>::d+1;};
template<class T>using core_t=vec_attr<T>::core_type;
template<class V>istream&operator>>(istream&i,vector<V>&v){fe(v,e)i>>e;return i;}
template<class V>ostream&operator<<(ostream&o,const vector<V>&v){fe(v,e)o<<e<<string(&e!=&v.back(),vectorial<V>?nl:sp);return o;}

template<class V>struct vec:vector<V>{
  using vector<V>::vector;
  vec(const vector<V>&v){vector<V>::operator=(v);}

  vec&operator^=(const vec&u){this->insert(this->end(),u.begin(),u.end());return*this;}
  vec operator^(const vec&u)const{return vec{*this}^=u;}
  vec&operator++(){fe(*this,e)++e;return*this;}
  vec&operator--(){fe(*this,e)--e;return*this;}
  vec operator-()const{vec v=*this;fe(v,e)e=-e;return v;}

  auto lower_bound(const V&x)const{return std::lower_bound(this->begin(),this->end(),x);}
  ll arglb(const V&x)const{return lower_bound(x)-this->begin();}
};
template<class T=ll,size_t n,size_t i=0>auto make_vec(const ll(&s)[n],T x={}){if constexpr(n==i+1)return vec<T>(s[i],x);else{auto X=make_vec<T,n,i+1>(s,x);return vec<decltype(X)>(s[i],X);}}
template<ll n,class...A>void setsize(const ll(&l)[n],A&...a){((a=make_vec(l,core_t<A>())),...);}

void lin(auto&...a){(cin>>...>>a);}
void vin(auto&...a){fo(i,(a.size()&...))(cin>>...>>a[i]);}
template<char c=sp>void pp(const auto&...a){ll n=sizeof...(a);((cout<<a<<string(--n>0,c)),...);cout<<nl;}

auto zip(auto&...a){auto v=(a^...);unique(v);([&](auto&u){fe(u,e)e=v.arglb(e);}(a),...);return v;}

template<class T>struct factorial{
  ll M;
  vec<T>fa,fa_inv;
  factorial(ll M):M(M),fa(M+1),fa_inv(M+1){
    fa[0]=1;
    fo(i,1,M+1)fa[i]=fa[i-1]*i;
    fa_inv.back()=fa.back().inv();
    of(i,M)fa_inv[i]=fa_inv[i+1]*(i+1);
  }

  T operator()(ll n)const{assert(n<=M);return fa[n];}
  T inv(ll n)const{assert(n<=M);return fa_inv[n];}
};

template<class T>struct combination{
  ll M;
  factorial<T>fa;
  combination(ll M):M(M),fa(M){}
  T c(ll n,ll k){return n<0?pwm1(k)*c(-n+k-1,k):k<0||n<k?0:fa(n)*fa.inv(k)*fa.inv(n-k);}
  T p(ll n,ll k){return c(n,k)*fa(k);}
};

single_testcase
void solve(){
  LL(N,K);
  VV(N,a,b);

  auto v=zip(a,b);
  vec<vec<int>>g(v.size());
  fo(i,N){
    g[a[i]].eb(i);
    g[b[i]].eb(~i);
  }

  combination<ml>comb(K);
  ml ans=1;
  ll choice=K;
  fo(x,v.size()){
    ll c=0;
    fe(g[x],i){
      if(i>=0)c++;
      else choice++;
    }
    ans*=(choice>=0?comb.p(choice,c):0);
    choice-=c;
  }
  pp(ml{K}.pow(N)-ans);
}}