#include<bits/stdc++.h>
using namespace std;

typedef long long ll;


inline long long poww(long long x,long long y,long long mod){
	long long ret=1;
	while (y){
		if (y&1) ret=ret*x,ret%=mod;
		x*=x,x%=mod;
		y>>=1;
	}
	return ret;
}
inline long long inv(long long x,long long mod){return poww(x,mod-2,mod);}

const ll mod=998244353;
const ll inv2=(mod+1)/2;
ll inv6=inv(6,mod);

const int maxn=200000;
ll n,m;
pair<ll,ll> a[maxn+50];

pair<ll,ll> operator - (const pair<ll,ll> &A,const pair<ll,ll> &B){
    return make_pair(A.first-B.first,A.second-B.second);
}
__int128 cross(const pair<ll,ll> &A,const pair<ll,ll> &B){
    return (__int128)A.first*B.second-(__int128)A.second*B.first;
}

int main(){
    ios_base::sync_with_stdio(false);

    cin >> n >> m;
    for (ll i=1;i<=n;i++){
        cin >> a[i].first >> a[i].second;
        a[i].second+=i*(i+1)/2;
    }
    a[0]=make_pair(0LL,0LL);
    a[n+1]=make_pair(m,m*(m+1)/2);
    
    vector<pair<ll,ll>> stk;
    for (int i=0;i<=n+1;i++){
        while (stk.size()>=2 && cross(stk[stk.size()-1]-stk[stk.size()-2],a[i]-stk[stk.size()-1])>=0) stk.pop_back();
        stk.push_back(a[i]);
    }

//    for (auto [x,y]:stk) cerr << "(" << x << "," << y << ")" << endl;

    vector<pair<ll,ll>> vk;
    {
        int sz=(int)stk.size();
        for (int i=1;i<sz;i++){
            auto [x,y]=stk[i]-stk[i-1];
            bool flag=0;
            if (x<0){flag=1;x=-x;}
            ll k=y/x;
            ll r=y%x;
            if (!flag){
                if (r>0) vk.emplace_back(k+1,r);
                vk.emplace_back(k,x-r);
            }
            else{
                vk.emplace_back(-(k),x-r);
                if (r>0) vk.emplace_back(-(k+1),r);
            }
        }
    }
    sort(vk.begin(),vk.end(),greater<pair<ll,ll>>());

//    for (auto [k,cnt]:vk) cerr << k << "," << cnt << endl;

    __int128 presum=0;
    ll ans=0;
    for (auto [k,cnt]:vk){
        __int128 tmp=((presum+k)+(presum+k*cnt))*cnt/2;
        tmp=tmp%mod;
        if (tmp<0) tmp+=mod;
        ans=(ans+tmp)%mod;
        presum=(presum+k*cnt)%mod;
        if (presum<0) presum+=mod;
    }

    // for (ll i=1;i<=m;i++){
    //     ans=(ans+mod-(i*(i+1)/2)%mod)%mod;
    // }
    {
        ans=ans-(m+2)*(m+1)%mod*m%mod*inv6%mod;
        ans=ans%mod;
        if (ans<0) ans+=mod;
    }

    cout << ans << "\n";
    return 0;
}