Compilare: user.cpp: In function ‘int main()’: user.cpp:17:9: warning: unused variable ‘i’ [-Wunused-variable] int i,N,f1,f2,f3; ^ user.cpp:17:13: warning: unused variable ‘f1’ [-Wunused-variable] int i,N,f1,f2,f3; ^ user.cpp:17:16: warning: unused variable ‘f2’ [-Wunused-variable] int i,N,f1,f2,f3; ^ user.cpp:17:19: warning: unused variable ‘f3’ [-Wunused-variable] int i,N,f1,f2,f3; ^ user.cpp:14:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fibo2.in","r",stdin); ^ user.cpp:15:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("fibo2.out","w",stdout); ^ user.cpp:19:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^