"use strict";

function main(arg) {
    //    console.log(arg.trim().split("\n"));
    let ary = arg.trim().split(" ").map(n => Number(n));
    let sheep = ary.shift();
    let wolf = ary.shift();
    console.log(wolf >= sheep ? 'unsafe' : 'safe');

}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));