Compilare: user.cpp: In function 'int pairup(int)': user.cpp:78: warning: comparison between signed and unsigned integer expressions user.cpp:87: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void solve_problem(int)': user.cpp:103: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int main()': user.cpp:148: warning: comparison between signed and unsigned integer expressions