```
import sys
sum=0
valid=True
for i in sys.argv[1:]:
    if i.isnumeric():
        if int(i) % 2 == 0:
            sum+=int(i)
    else:
        print("Error: invalid input, expecting a list of numbers")
        valid=False

if valid==True:
    print(sum)   
```
```
import sys
sum=0
valid=True
for i in sys.argv[1:]:
    if i.isnumeric():
        if int(i) % 2 == 0:
            sum+=int(i)
    else:
        print("Error: invalid input, expecting a list of numbers")
        valid=False

if valid==True:
    print(sum)   
```