function main(input) {
  let [a,b,c,d] = input.split(' ').map(Number)
  let i = 0
  let str = ''
  while(a > 0 && c > 0) {
    if (i % 2 === 0) {
      c = c - b
      str = 'Yes'
    } else {
      a = a - d
      str = 'No'
    }
    i++
  }
  console.log(str)
}

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