Compilare: main.cpp: In function 'void setIO(std::__cxx11::string, bool, bool)': main.cpp:7:51: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] if(input) freopen(inputname.c_str(), "r", stdin); ^ main.cpp:8:54: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] if(output) freopen(outputname.c_str(), "w", stdout); ^ main.cpp: In function 'int main()': main.cpp:53:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ main.cpp:55:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &A[0], &B[0], &C[0]); ^