Compilare: user.cpp: In function ‘void ReadInput()’: user.cpp:20:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &N, &M); graph.resize(N); ^ user.cpp:23:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int u, v; scanf("%d%d", &u, &v); u--; v--; ^