Compilare: user.cpp: In function ‘void backt(int)’: user.cpp:15:8: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (!ok) ^ user.cpp: In function ‘int main()’: user.cpp:58:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, x, y, k=0; ^ user.cpp:60:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &n, &m, &nr); ^ user.cpp:63:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^