#include<bits/stdc++.h>
using namespace std;

int main()
{
	int y,l;
	cin >> y >> l;
	
	if(y>l)
	{
		cout << "safe" << endl;
		return 0;
	}
	else if(l>y)
	{
		cout << "unsafe" << endl;
		return 0;
	}
	else if(l=y)
	{
		cout << "unsafe" << endl;
		return 0;
	}
} 