'use strict'

function main(input) {
  input = input.trim().split('\n')
  const N = ~~input[0]
  if (N === 1) {
    console.log('Yes')
    return
  }
  const memo = [0]
  const nums = input[1].split(' ').map(v => ~~v)
  let ans = 'Yes'
  for (let i = 0; i < N; i++) {
    //
    memo.push(nums[i + 1] - nums[i] + memo[i])
    if (memo[i + 1] > i + 1) {
      ans = 'No'
      console.log(ans)
      return
    }
  }
  console.log(ans)
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'))
