Compilare: main.cpp: In function 'void dfs_cnt(int)': main.cpp:22:13: warning: unused variable 'cost' [-Wunused-variable] int cost = e.second; ^~~~ main.cpp: In function 'int main()': main.cpp:49:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("halftree.in", "r", stdin); ^ main.cpp:50:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("halftree.out", "w", stdout); ^