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

#define fr(i,n) for(int i = 0; i<n; i++)
#define sz(v) (int)(v.size())
#define prin(a) cout << #a << " = " << a << endl
#define all(v) (v).begin(),(v).end()
typedef long long ll;

int main(){
	ll s, w;
	scanf("%lld%lld", &s, &w);
	if(w>=s) puts("unsafe");
	else puts("safe");
}