Compilare: user.cpp: In function ‘int main()’: user.cpp:57:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix2.in", "r", stdin); ^ user.cpp:58:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix2.out", "w", stdout); ^ user.cpp:60:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", str + 1); n = strlen(str + 1); ^