Compilare: user.cpp: In function 'void debug()': user.cpp:23: warning: comparison between signed and unsigned integer expressions user.cpp:26: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void build()': user.cpp:45: warning: comparison between signed and unsigned integer expressions user.cpp:45: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void solve()': user.cpp:99: warning: comparison between signed and unsigned integer expressions user.cpp:102: warning: comparison between signed and unsigned integer expressions user.cpp:110: warning: comparison between signed and unsigned integer expressions user.cpp:113: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void read_data()': user.cpp:145: warning: comparison between signed and unsigned integer expressions