Compilare: user.cpp: In function ‘int main()’: user.cpp:21:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("piete.in","r",stdin); ^ user.cpp:22:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("piete.out","w",stdout); ^ user.cpp:23:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d", &n,&m,&s,&f); ^ user.cpp:25:48: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(j=1;j<=m;++j) scanf("%d", &a[i][j]); ^