foo.cc: In function 'bool prime(int)':
foo.cc:6:13: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    6 |  if(x<2||x>2&&x%2==0) return 0;
      |          ~~~^~~~~~~~
foo.cc: In function 'void dfs(int, int, int)':
foo.cc:18:13: error: 'f' was not declared in this scope
   18 |     if(s>n||f) return ;
      |             ^
foo.cc:22:3: error: 'f' was not declared in this scope
   22 |   f=1;
      |   ^

Found 10 testcases.