Compilare: user.cpp: In function 'bool valid(int)': user.cpp:37: warning: comparison between signed and unsigned integer expressions user.cpp:46: warning: comparison between signed and unsigned integer expressions user.cpp:46: warning: comparison between signed and unsigned integer expressions user.cpp:49: warning: comparison between signed and unsigned integer expressions user.cpp:34: warning: unused variable 'step' user.cpp:34: warning: unused variable 'i' user.cpp:34: warning: unused variable 'S' user.cpp:34: warning: unused variable 'D1' user.cpp: In function 'void solve()': user.cpp:67: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void cit()': user.cpp:88: warning: comparison between signed and unsigned integer expressions