#include<bits/stdc++.h>
using namespace std;
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		int x,y,z;
		cin>>x>>y>>z;
		if(x+y>z&&x+y-z>z) cout<<x+y-z<<endl;
		else if(x+y==z) cout<<z+2<<endl;
		else cout<<-1<<endl;
	}
    return 0;
}