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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. int main() {
  4. 	uint64_t n, a, b; cin >> n >> a >> b;
  5. 	multiset<uint64_t> s;
  6. 	for (uint64_t m=1<<n;m;m /= 2) { if (a&m) s.insert(m); if (b&m) s.insert(m); }
  7. 	int ans = 0;
  8. 	while (*s.begin() != (1 << n)) {
  9. 		auto first = s.begin(), second = next(first);
  10. 		if (second != s.end() && *first == *second) {
  11. 			uint64_t nxt = *first + *second;
  12. 			s.erase(first); s.erase(second);
  13. 			s.insert(nxt);
  14. 		} else {
  15. 			uint64_t nxt = *first * 2;
  16. 			s.erase(first);
  17. 			s.insert(nxt);
  18. 		}
  19. 		++ans;
  20. 	}
  21. 	if (s.size() == 1) {
  22. 		cout << ans << endl;
  23. 	} else {
  24. 		cout << "impossible" << endl;
  25. 	}
  26. }
  27.  
Success #stdin #stdout 0s 16064KB
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https://ideone.com/xEhb2a
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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