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

char*mmap();
#define rd(v) long v=0;{int _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 MD     998244353
#define inv24  291154603

int t[300001];
int v[300001];

main(){
	long s=0,l=0,r=0;
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rep(i,n){
		rd(ti);
		s+=ti%=MD;
		t[i]=ti;
		rd(vi);
		v[i]=vi;
	}
	s%=MD;
	rep(i,n){
		l+=t[i];
		l-=l>=MD?MD:0;
		r+=l*(l+1)%MD*(l+2)%MD*(s*4-(l-1)*3)%MD*(v[i]-v[i+1])%MD;
	}
	r=r%MD*inv24%MD;
	r+=r>=0?0:MD;

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