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

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

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