#include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
using ll = long long;
using P = pair<int,int>;
ll gcd(ll a, ll b) { return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}




int main()
{
    int S,W;
    cin >> S >> W;
    string str;
    if(W >= S) str = "unsafe";
    else str = "safe";

    cout << str << endl;

    return 0;
}
//Ctrl+Shift+Bでコンパイルと実行を行ってデバッグすること