Compilare: user.cpp: In function ‘int main()’: user.cpp:104:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("shuffle2.in","r",stdin); ^ user.cpp:105:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("shuffle2.out","w",stdout); ^ user.cpp:106:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:118:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^ user.cpp: In function ‘long long int C(int, int)’: user.cpp:38:1: warning: control reaches end of non-void function [-Wreturn-type] } ^