function main(input) {
    const args = input.split(' ');
    const s = parseInt(args[0], 10);
    const w = parseInt(args[1], 10);

    if ( w >= s ) {
        console.log('unsafe');
    } else {
        console.log('safe');
    }
}

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