t0yv0

let euler19 () =
    let mutable k = 0
    for y in 1901 .. 2000 do
        for m in 1 .. 12 do
            let date = System.DateTime(y, m, 1)
            if date.DayOfWeek = System.DayOfWeek.Sunday then
                k <- k + 1
    k

stdout.WriteLine(euler19 ())