求hack

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,i,x,j,y,k,ans=INT_MAX;
	cin>>n;
	x=n;
	for(i=2;i*i<=x;i++)
		if(x%i==0){
			while(x%i==0)
				x/=i;
			for(j=n-i+1;j<n;j++){
				y=j;
				for(k=2;k*k<=y;k++)
					if(y%k==0){
						while(y%k==0)
							y/=k;
						if(j-k+1<ans){
							ans=j-k+1;
//							cout<<"i="<<i<<" j="<<j<<" k="<<k<<" ans="<<ans<<endl;
						}
					}
				if(y>1 && y<j && j-y+1<ans){
					ans=j-y+1;
//							cout<<"i="<<i<<" j="<<j<<" y="<<y<<" ans="<<ans<<endl;
				}
				if(y==j && y<ans)
					ans=y;
			}
		}
	if(x>1){
		for(j=n-x+1;j<n;j++){
			y=j;
			for(k=2;k*k<=y;k++)
				if(y%k==0){
					while(y%k==0)
						y/=k;
					if(j-k+1<ans){
						ans=j-k+1;
//							cout<<"x="<<x<<" j="<<j<<" k="<<k<<" ans="<<ans<<endl;
					}
				}
			if(y>1 && y<j && j-y+1<ans){
				ans=j-y+1;
//				cout<<"x="<<x<<" j="<<j<<" y="<<y<<" ans="<<ans<<endl;
			}
			if(y==j && y<ans)
				ans=y;
		}
	}
	if(ans==INT_MAX)
		cout<<-1;
	else
		cout<<ans;
	return 0; 
}