Compilare: user.cpp: In function ‘int pairup(int)’: user.cpp:15: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void df(int, int)’: user.cpp:51: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:96: warning: comparison between signed and unsigned integer expressions user.cpp:71: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:72: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:73: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:78: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result