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F. Primes in Interval

time limit per test

2 secondsmemory limit per test

64 megabytesinput

standard inputoutput

standard outputYou are given two integers *a* and *b* (*a* ≤ *b*). How many prime numbers are there on the interval from *a* to *b*, inclusive?

Input

The input contains two integers *a* and *b* (2 ≤ *a* ≤ *b* ≤ 1 000 000), separated by a single space.

Output

Output a single integer — the number of primes between *a* and *b*, inclusive.

Examples

Input

10 20

Output

4

Input

23 23

Output

1

Input

271 566

Output

46

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