Compilare: user.cpp: In function ‘long long int r(int)’: user.cpp:16:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^ user.cpp: In function ‘int main()’: user.cpp:38:13: warning: unused variable ‘nr1’ [-Wunused-variable] int n , nr1,nr2,i; ^ user.cpp:38:17: warning: unused variable ‘nr2’ [-Wunused-variable] int n , nr1,nr2,i; ^ user.cpp:36:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("perechi.in","r",stdin); ^ user.cpp:37:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("perechi.out","w",stdout); ^ user.cpp:40:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^