Compilare: user.cpp: In function ‘int main()’: user.cpp:24:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("kdrum.in","r",stdin); ^ user.cpp:25:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("kdrum.out","w",stdout); ^ user.cpp:29:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&N,&M,&K); ^ user.cpp:30:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d",&x0,&y0,&x1,&y1); ^ user.cpp:32:53: 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",&v[i][j]); ^