Compilare: user.cpp: In function ‘int main()’: user.cpp:49:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < sol.size(); i++) ^ user.cpp:8:24: warning: unused variable ‘j’ [-Wunused-variable] int N, M, x, y, i, j, k; ^ user.cpp:8:27: warning: unused variable ‘k’ [-Wunused-variable] int N, M, x, y, i, j, k; ^