let i = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n').slice(0, -1)
let s = i[0]
for (let x = 2; x < i.length; x++) {
  if (i[x].indexOf(s) > -1) {
    for (let c of i[x].split(' ')) {
      if (c !== s) {
        s = c
        break
      }
    }
  }
}
console.log(s)