Compilare: user.cpp: In function ‘void solve()’: user.cpp:19: warning: unused variable ‘change’ user.cpp:20: warning: unused variable ‘first’ user.cpp: In function ‘int main()’: user.cpp:57: warning: comparison between signed and unsigned integer expressions user.cpp:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:47: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:50: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:54: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result