"use strict";
function main(input) {
  let s = 0;
  let w = 0;
  [s, w] = input[0].trim().split(" ").map(i => parseInt(i));
  
  console.log((s<=w)?"unsafe":"safe");
 
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"));