flag="*********"
def RabinKarpRollingHash( str, a, n ):
result = 0
l = len(str)
for i in range(0, l):
result += ord(str[i]) * a ** (l - i - 1) % n
print "result = ", result
RabinKarpRollingHash(flag, 256, 10**30)

output is
1317748575983887541099
What is the flag?