function main(input) {
    var split = input.split(" ");
    var sheep = parseInt(split[0]);
    var elf = parseInt(split[1]);
    if (sheep > elf) {
     console.log("safe");
    } else if (sheep <= elf){
     console.log("unsafe");
    }

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