Compilare: user.cpp: In function ‘bool isGood(char*)’: user.cpp:10:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < strlen(input); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:31:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < strlen(s) - 1; i++) { ^ user.cpp:32:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i + 1; j < strlen(s); j++) { ^ user.cpp:29:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in,"%s",s); ^