#include<bits/stdc++.h>
#define eps 1e-9
#define MOD 1000000007
#define INV_10 299473306
#define INF 1000000000
using namespace std;
int main()
{
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	int s, w;
	cin >> s >> w;
	cout << ((w>=s) ? ("unsafe\n") : ("safe\n"));
}