Compilare: user.cpp: In function ‘int main()’: user.cpp:37:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i<a[k].size(); i++) ^ user.cpp:20:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, x, y, p, u, k; ^ user.cpp:20:21: warning: unused variable ‘p’ [-Wunused-variable] int i, j, x, y, p, u, k; ^ user.cpp:20:24: warning: unused variable ‘u’ [-Wunused-variable] int i, j, x, y, p, u, k; ^