求助RE

#include<bits/stdc++.h>
#define int long long
#define N 20000000
using namespace std;
int a[N],vis[N];
bool _7(int x)
{
	while(x)
	{
		if(x%10==7) return true;
		x/=10;
	}
	return false;
}
signed main()
{
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
	int n,i,j,sum=0,t;
	cin>>n;
	for(i=1;i<=N;i++)
	{
		if(!vis[i])
		{
			if(_7(i))
			{
				for(j=1;i*j<=N;j++) vis[i*j]=-1;
			}
			else vis[i]=++sum,a[sum]=i;
		}
	}
	for(i=1;i<=n;i++)
	{
		cin>>t;
		if(vis[t]==-1) cout<<-1<<endl;
		else cout<<a[vis[t]+1]<<endl;
	}
	return 0;
}