def int2fin_reference(n):
checksum = <NUM_LIT:10> - (sum([int(c) * i for c, i in zip(str(n)[::-<NUM_LIT:1>], it.cycle((<NUM_LIT:7>, <NUM_LIT:3>, <NUM_LIT:1>)))]) % <NUM_LIT:10>)<EOL>if checksum == <NUM_LIT:10>:<EOL><INDENT>checksum = <NUM_LIT:0><EOL><DEDENT>return "<STR_LIT>" % (n, checksum)<EOL>
Calculates a checksum for a Finnish national reference number