petrol_pump.py

fuel = map(lambda x:int(x), raw_input().split())
distance = map(lambda x:int(x), raw_input().split())

# takes the standard input as space separated integers in two lines.

diff = [b-a for b,a in zip(fuel, distance)] # creates the diff array
diff = diff + diff  # to account for cyclic array

start = 0 # let say we start from 0 the position
end = 0
summation = 0
counter = 0 # keeps the count of petrol pumps accessed
for i in range(len(diff)):
    if(end - start >= len(distance)):
        break; 
    summation += diff[i]
    end += 1
    if(summation < 0):
        summation = 0
        start +=1
        end = start

if(end - start == len(distance)): # we covered exactly 5 petrol pumps
    print start
else:
    print "solution doesn't exist"