Compilare: user.cpp: In function ‘int main()’: user.cpp:55:11: warning: unused variable ‘l’ [-Wunused-variable] int i,l,c=0; char aux[20]; ^ user.cpp:55:13: warning: unused variable ‘c’ [-Wunused-variable] int i,l,c=0; char aux[20]; ^ user.cpp:55:23: warning: unused variable ‘aux’ [-Wunused-variable] int i,l,c=0; char aux[20]; ^ user.cpp:51:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("euler.in","r",stdin); ^ user.cpp:52:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("euler.out","w",stdout); ^ user.cpp:53:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&N); ^ user.cpp:66:47: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (i=1; i<=2*N-1; i++) scanf("%d",&a[i]); ^