赛后：

#include<bits/stdc++.h>
using namespace std;
int n;
int b[]={0,108,188,200,208,288,688,888};
int a[]={10,18,22,20,28,68,88,108,188,200,208,288,688,888,1088,1888,2008,2088,2888,6888,8888,10888,18888,20088,20888,28888,68888,88888,108888,188888,200888,208888,288888,688888,888888,1088888,1888888,2008888,2088888,2888888,6888888,8888888,10888888,18888888,20088888};
int main()
{
	std::ios::sync_with_stdio(0),cin.tie(0);
	int t;
	cin>>t;
	while(t--)
	{
		cin>>n;
		if(n==1)
			cout<<-1<<"\n";
		else if(n==2)
			cout<<1<<"\n";
		else if(n==3)
			cout<<7<<"\n";
		else if(n==4)
			cout<<4<<"\n";
		else if(n==5)
			cout<<2<<"\n";
		else if(n==6)
			cout<<6<<"\n";
		else if(n==7)
			cout<<8<<"\n";
		else if(n<=50)
			cout<<a[n-8]<<"\n";
		else if(n%7==0)
		{
			for(register int i=1;i<=n/7;i++)
				cout<<8;
			cout<<"\n";
		}
		else if(n%7==1)
		{
			cout<<10;
			for(register int i=1;i<=n/7-1;i++)
				cout<<8;
			cout<<"\n";
		}
		else 
		{
			cout<<b[n%7];
			for(register int i=1;i<=n/7-2;i++)
				cout<<8;
			cout<<"\n";
		}
	}
	return 0;
}

赛中

#include<bits/stdc++.h>
using namespace std;
int n;
int b[]={0,108,188,200,208,288,688,888};
int a[]={10,18,22,20,28,68,88,108,188,200,208,288,688,888,1088,1888,2008,2088,2888,6888,8888,10888,18888,20088,20888,28888,68888,88888,108888,188888,200888,208888,288888,688888,888888,1088888,1888888,2008888,2088888,2888888,6888888,8888888,10888888,18888888,20088888};
int main()
{
	std::ios::sync_with_stdio(0),cin.tie(0);
	int t;
	cin>>t;
	while(t--)
	{
		cin>>n;
		if(n==1)
			cout<<-1<<"\n";
		else if(n==2)
			cout<<1<<"\n";
		else if(n==3)
			cout<<7<<"\n";
		else if(n==4)
			cout<<4<<"\n";
		else if(n==5)
			cout<<2<<"\n";
		else if(n==6)
			cout<<6<<"\n";
		else if(n==7)
			cout<<8<<"\n";
		else if(n<=50)
			cout<<a[n-8]<<"\n";
		else if(n%7==0)
		{
			for(register int i=1;i<=n/7-1;i++)
				cout<<8;
			cout<<"\n";
		}
		else if(n%7==1)
		{
			cout<<10;
			for(register int i=1;i<=n/7-1-1;i++)
				cout<<8;
			cout<<"\n";
		}
		else 
		{
			cout<<b[n%7];
			for(register int i=1;i<=n/7-2-1;i++)
				cout<<8;
			cout<<"\n";
		}
	}
	return 0;
}

细品，你细品，
不说了，换眼角膜去了