param(
    [Parameter(Mandatory=$true)]
    [string]$LogName
)

if (-not (Get-WinEvent -ListLog $LogName -ErrorAction SilentlyContinue)) {
    Write-Error "Event log '$LogName' does not exist."
    exit 1
}

$start = (Get-Date).AddHours(-1)
# 1:Critical, 2: Error, 3: Warning, 4: Information, 5: Verbose
$count = (Get-WinEvent -FilterHashtable @{
    LogName = $LogName
    Level   = 1,2
    StartTime = $start
} -ErrorAction SilentlyContinue).Count

Write-Output $count
exit 0