#include<bits/stdc++.h>
#define ll long long
#define ull __int128
using namespace std;
const int N=2e5+10,mod=998244353;
const ull inf=2e18;
struct node{
  ull x,y,d;
};
node st[N];
int top;
int n,m,res;
struct put{
  ll x,y;
}p[N];
ull ans;
ull calc(ull h,ull len,ull d){return (h+h+(len-1)*d)*len/2;}
ull calc2(ull d,ull len){return d*len*len+(len-1)*len*(len*2-1)/6-(len+d)*len*(len-1)/2;}
void write(ull x){
  if(x<0){putchar('-');x=-x;}
  if(x>9)write(x/10);
  putchar(x%10+'0');
}
void writesp(ull x){
  write(x);putchar(' ');
}
signed main(){
  ios::sync_with_stdio(0);
  cin.tie(0),cout.tie(0);
  cin>>n>>m;
  for(int i=1;i<=n;i++)cin>>p[i].x>>p[i].y;
  p[++n]=(put){0,0},p[++n]=(put){m,0};
  sort(p+1,p+1+n,[&](put x,put y){return x.x<y.x;});
  st[++top]=(node){0,0,inf};
  for(int i=2;i<=n;i++){
    ull d=0;
    while(top){
      node x=st[top];
      ull dis=p[i].x-x.x;
      if(x.y+calc(x.d-1,dis,-1)<p[i].y){top--;continue;}
      ull c=x.y+calc(x.d-1,dis,-1)-p[i].y;
      d=x.d-dis-(c-1)/dis-1;
      break;
    }
    st[++top]=(node){p[i].x,p[i].y,d};
  }
  for(int i=2;i<=top;i++){
    node x=st[i-1],y=st[i];
    ull dis=y.x-x.x,c=x.y+calc(x.d-1,dis,-1)-y.y;
    ans+=x.y*dis+calc2(x.d-1,dis);
    ull s=c/dis,r=c%dis;
    ans+=calc(-1,dis,-1)*s+calc(-1,r,-1);
  }
  res=ans%mod;
  cout<<res<<'\n';
  return 0;
}