Compilare: user.cpp: In function ‘int main()’: user.cpp:41:15: warning: unused variable ‘j’ [-Wunused-variable] int n,m,i,j,k,p,a,b,ans=0; ^ user.cpp:41:17: warning: variable ‘k’ set but not used [-Wunused-but-set-variable] int n,m,i,j,k,p,a,b,ans=0; ^ user.cpp:39:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marvel.in","r",stdin); ^ user.cpp:40:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marvel.out","w",stdout); ^ user.cpp:43:41: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(si+1,chmax,sizeof(char),stdin); ^