Compilare: user.cpp: In function ‘void back(int)’: user.cpp:23:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<v[i].size(); j++) ^ user.cpp:26:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<v[i].size(); j++) ^ user.cpp: In function ‘int main()’: user.cpp:33:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pluricex.in","r",stdin); ^ user.cpp:34:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pluricex.out","w",stdout); ^ user.cpp:35:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&n,&k,&d); ^ user.cpp:38:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a); ^ user.cpp:41:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&b); ^