#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <vector>
#include <algorithm>
#include <math.h>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>

#define _GLIBCXX_DEBUG
#define rep(i, n) for (int64_t i = 0; i < (int64_t)(n); i++)
using namespace std;
using vi = vector<int64_t>;
using vvi = vector<vi>;

int main(int argc, const char * argv[]) {
    // fasten cin
    cin.tie(0);
    ios::sync_with_stdio(false);
    // implement
    int64_t s, w;
    cin >> s >> w;
    string res = w >= s ? "unsafe" : "safe";
    cout << res << endl;
}
