#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
using Map = map<string,ll>;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
ll INF=1LL<<60;
ll MOD=1000000007;

int main(){
    ll k=0;
    for(ll i=0;i<10000000000;i++){k++;
    ;}
    ll S;
    cin >> S;
    ll W;
    cin >> W;
    if(S<=W)cout<<"unsafe"<<endl;
    else cout<<"No"<<endl;
    return 0;
}
