func main[] : I64
    let sum: I64 = 0
    let a: I64 = 0
    let b: I64 = 1

    while a < 4000000
        if a % 2 == 0
            sum = sum + a
        let temp: I64 = b
        b = a + b
        a = temp

    io.print_i64(sum)