# Input 4 numbers
a, b, c, d = [int(input("Enter a number: ")) for i in range(4)]

# Check if numbers are positive or negative
sum_of_positive_numbers = 0
for num in [a, b, c, d]:
    if num >= 0:
        sum_of_positive_numbers += num
    else:
        print(f"{num} is negative")

# Calculate the sum of positive numbers
if sum_of_positive_numbers > 0:
    print(f"Sum of positive numbers: {sum_of_positive_numbers}")
else:
    print("All numbers are negative")