Compilare: main.cpp: In function 'int main()': main.cpp:140:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("xsizero.in","r",stdin); ^ main.cpp:141:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("xsizero.out","w",stdout); ^ main.cpp: In function 'int f(char)': main.cpp:136:1: warning: control reaches end of non-void function [-Wreturn-type] } ^