let i = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n')[1].split(' ').map((e) => parseInt(e))
let t = i.reduce((p,c) => p + c)
if (t % 2 == 1) console.log('impossible')
else {
  let r = []
  let h = t / 2
  let f = false
  for (let x of i) {
    let c = r.concat()
    c.push(x)
    r = r.map((e) => e+x)
    r = r.filter((e) => e <= h)
    r = r.concat(c)
    if (r.indexOf(h) > -1) {
      f = true
      break
    }
  }
  console.log(f ? 'possible' : 'impossible')
}