# function that reads population file and builds
# dictionary
def makeDictionary():
    return {}

# function that reads drinking water file and prints out
# countries that have changed percentage of people with
# access, if population is big enough.
def readDWdata(popDict):
    return

def main():

     # Build dictionary from population file
     popDict = makeDictionary()

     # Read file containing drinking water data. 
     # Print out change for large enough contries
     readDWdata(popDict)
     
main()