Compilare: user.cpp: In function ‘bool pairup(int)’: user.cpp:86: warning: comparison between signed and unsigned integer expressions user.cpp:93: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:104: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:105: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:109: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:112: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result /tmp/ccnn8eie.o: In function `main': user.cpp:(.text+0x2ac): warning: the `gets' function is dangerous and should not be used.