/in/foo.cc: In function 'int main()':
/in/foo.cc:131:28: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markr[i] & (1 << x - 1)) markr[i] ^= (1 << x - 1);
                          ~~^~~
/in/foo.cc:131:54: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markr[i] & (1 << x - 1)) markr[i] ^= (1 << x - 1);
                                                    ~~^~~
/in/foo.cc:132:28: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markc[j] & (1 << x - 1)) markc[j] ^= (1 << x - 1);
                          ~~^~~
/in/foo.cc:132:54: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markc[j] & (1 << x - 1)) markc[j] ^= (1 << x - 1);
                                                    ~~^~~
/in/foo.cc:133:38: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markb[block[i][j]] & (1 << x - 1)) markb[block[i][j]] ^= (1 << x - 1);
                                    ~~^~~
/in/foo.cc:133:74: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
     if (markb[block[i][j]] & (1 << x - 1)) markb[block[i][j]] ^= (1 << x - 1);
                                                                        ~~^~~