Compilare: user.cpp: In function ‘int main()’: user.cpp:34:13: warning: unused variable ‘w’ [-Wunused-variable] int x,y,z,w; ^ user.cpp:30:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bellmanford.in","r",stdin); ^ user.cpp:31:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bellmanford.out","w",stdout); ^ user.cpp:33:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d ",&N,&M); ^ user.cpp:36:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d ",&x,&y,&z); ^