Compilare: user.cpp: In function ‘void solve(int)’: user.cpp:30:15: warning: unused variable ‘k’ [-Wunused-variable] int i, j, k; ^ user.cpp: In function ‘int main()’: user.cpp:169:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tree2.in","r",stdin); ^ user.cpp:170:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tree2.out","w",stdout); ^ user.cpp:172:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:174:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^