def selection_sort(arr):
    n = len(arr)
    for i in range(n - 1):
        # Assume the current element is the smallest
        min_index = i

        # Checking the rest of the array to find the smallest one
        for j in range(i + 1, n):
            if arr[j] < arr[min_index]:
                min_index = j   # Update the index of the smallest number

        # If the smallest number is not the first, replace
        if min_index != i:
            arr[i], arr[min_index] = arr[min_index], arr[i]

# Example:

nums = [5, 2, 4, 6, 1, 3]
print("Before sorting:", nums)

selection_sort(nums)
print("After sorting:", nums)