'use strict'

const main = (INPUT) => {
  const W = INPUT.split('\n').slice(1)

  let ans = 'Yes'
  for (let i = 1; i < W.length; i++) {
    let e = W[i - 1].slice(-1)
    let f = W[i].slice(0, 1)
    if (e != f) {
      ans = 'No'
      break
    }
    for (let j = 0; j < i; j++) {
      if (W[i] == W[j]) {
        ans = 'No'
        break
      }
    }
  }
  console.log(ans)
}

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