Compilare: user.cpp: In function ‘int main()’: user.cpp:145:17: warning: unused variable ‘c’ [-Wunused-variable] int x,y,c=1; ^ user.cpp:166:14: warning: unused variable ‘n’ [-Wunused-variable] for(auto n : g[X]){ ^ user.cpp:136:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("test.in","r",stdin); ^ user.cpp:137:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("test.out","w",stdout); ^