Compilare: user.cpp: In function ‘int main()’: user.cpp:147:17: warning: unused variable ‘c’ [-Wunused-variable] int x,y,c=1; ^ user.cpp:168:14: warning: unused variable ‘n’ [-Wunused-variable] for(auto n : g[X]){ ^ user.cpp:137:33: 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:138:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("atac2.out","w",stdout); ^ user.cpp:140:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d",&N,&M,&U,&X); ^ user.cpp:143:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^ user.cpp:148:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^