coins.cpp:14:17: error: '__gnu_pbds' is not a namespace-name
14 | using namespace __gnu_pbds;
| ^~~~~~~~~~
coins.cpp:15:9: error: 'tree' does not name a type; did you mean 'free'?
15 | typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
| ^~~~
| free
coins.cpp: In function 'std::vector<int> coin_flips(std::vector<int>, int)':
coins.cpp:19:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
19 | for(int i = 0; i < b.size(); i++) {
| ~~^~~~~~~~~~
coins.cpp: In function 'int find_coin(std::vector<int>)':
coins.cpp:29:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | for(int i = 0; i<b.size(); i++)
| ~^~~~~~~~~