Compilare: user.cpp: In function ‘int main()’: user.cpp:2:14: warning: suggest parentheses around ‘-’ inside ‘<<’ [-Wparentheses] #define MOD 1<<20-1 ^ user.cpp:16:35: note: in expansion of macro ‘MOD’ v[i]=(v[i-3]+v[i-1]+2*(i-2))&MOD; ^ user.cpp:11:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("12perm.in","r",stdin); ^ user.cpp:12:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("12perm.out","w",stdout); ^ user.cpp:13:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^