'use strict';
const main = arg => {
  const input = arg.trim().split(' ');
  const S = parseInt(input[0], 10);
  const W = parseInt(input[1], 10);

  if (S > W) {
    console.log('safe');
  }else {
    console.log('unsafe')
  }
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));