#include<bits/stdc++.h>
using namespace std;
#define FOR(i,l,r) for(long long i=(l);i<(r);++i)
#define REP(i,n) FOR(i,0,n)
#define int long long
const int MOD=1e9+7;
const int INF=1e15;

signed main(){
    int S,W;cin>>S>>W;
    if(W>=S)cout<<"unsafe"<<endl;
    else cout<<"safe"<<endl;
}