Compilare: user.cpp: In function ‘int main()’: user.cpp:19:32: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s2[strlen(s2) - 1] = NULL; ^ user.cpp:14:9: warning: unused variable ‘l’ [-Wunused-variable] int l = strlen(s) * 2; ^ user.cpp:9:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("beep.in", "r", stdin); ^ user.cpp:10:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("beep.out", "w", stdout); ^ user.cpp:11:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s\n", s); ^ user.cpp:12:25: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s1,1005,stdin); ^