Compilare: user.cpp: In function ‘void backt(int)’: user.cpp:16:7: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(ok==0) ^ user.cpp: In function ‘int main()’: user.cpp:48:15: warning: unused variable ‘j’ [-Wunused-variable] int x,y,i,j; ^