Compilare: user.cpp: In function ‘int main()’: user.cpp:39:10: warning: statement has no effect [-Wunused-value] for(i; i <= n ; ++i){ ^ user.cpp:25:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("kprime.in", "r", stdin); ^ user.cpp:26:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("kprime.out", "w", stdout); ^ user.cpp: In function ‘int getnum()’: user.cpp:9:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", s); ^