Compilare: user.cpp: In function ‘bool ok(int)’: user.cpp:29:15: warning: suggest parentheses around ‘-’ inside ‘<<’ [-Wparentheses] int j=1<<s-1; ^ user.cpp:30:12: warning: suggest parentheses around comparison in operand of ‘^’ [-Wparentheses] if (y^k==j) return true; ^ user.cpp: In function ‘int main()’: user.cpp:69:9: warning: unused variable ‘x’ [-Wunused-variable] int x, xt, yt; ^