Compilare: user.cpp: In function ‘void op1(int)’: user.cpp:11: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void op2(int)’: user.cpp:20: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int op3(int)’: user.cpp:33: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:44: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:47: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result