You've built an amazing fish-catching robot, but you've discovered one small flaw: the robot can't decide whether to fish or cut bait.
You've designed a language for the Control of Oceangoing Devices (COD) which you plan to use to program the robot. COD has three instructions:
| fish | Fish for ten minutes. |
|---|---|
| bait | Cut bait for ten minutes. |
| lunch | No operation for ten minutes. |
Bait is required to catch fish. The robot must cut bait for twenty minutes (execute two bait instructions) to generate a single bait unit, enough bait to catch a single fish. Other instructions (fish and lunch) may be interleaved between the two bait instructions that generate a bait unit. The robot has storage for three bait units; it cannot cut any more bait if it is already storing three bait units. If the robot is storing three bait units, a bait instruction is treated as if it were a lunch instruction (a NOP). Catching a fish consumes a bait unit.
Fish have deterministic behaviour. A fish cannot be caught more often than once every seventy minutes, and after a fish has been caught the robot must fish for thirty minutes before catching another fish (they get shy). In order to successfully complete a fish instruction, the robot must have a least one bait unit. If the robot has no bait, a fish instruction cannot be successfully completed and is treated as if it were a lunch instruction. When the robot first starts fishing, a fish is caught on the first fish instruction that completes (beginner's luck). If at least one fish has already been caught then a fish is caught on the completion of a fish instruction if and only if: 1) the fish instruction is at least the seventh COD instruction executed since the last instruction on which a fish was caught, and 2) the fish instruction is at least the third fish instruction successfully completed since the last instruction on which a fish was caught.
The execution of a lunch instruction allows time to pass, but has no other purpose.
The robot starts with no bait; no fish have been caught. Input consists of a sequence of fish, bait and lunch instructions, terminated by the end-of-file. Output is a line containing a single integer, indicating the number of fish the robot has caught at the end of the sequence.
fish fish lunch bait fish bait fish bait bait fish fish fish fish lunch lunch lunch lunch fish fish fish
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