Compilare: main.cpp: In function 'void read()': main.cpp:14:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.in","r",stdin); ^ main.cpp:15:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ main.cpp:17:50: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf",&x[i] ,&y[i]);// f>>x[i]>>y[i]; ^ main.cpp: In function 'void write()': main.cpp:37:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.out" , "w", stdout); ^