Compilare: user.cpp: In function ‘void build_graph()’: user.cpp:73:36: warning: narrowing conversion of ‘idx[j]’ from ‘int’ to ‘char’ inside { } [-Wnarrowing] l[i].pb({k,p[idx[j]],idx[j]}),used[k]=i+1; ^ user.cpp: In function ‘void read()’: user.cpp:38:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); ^ user.cpp:43:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&p[i],&nrc); ^ user.cpp:48:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^ user.cpp: In function ‘int main()’: user.cpp:121:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("boom.in","r",stdin); ^ user.cpp:122:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("boom.out","w",stdout); ^