Compilare: user.cpp: In function ‘int pairup(int)’: user.cpp:19: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:113: warning: suggest explicit braces to avoid ambiguous ‘else’ user.cpp:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:52: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:53: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result