foo.cc:25:39: warning: bad option '-fwhole-program' to pragma 'optimize' [-Wpragmas]
 #pragma GCC optimize("-fwhole-program")
                                       ^
foo.cc:34:41: warning: bad option '-fcse-skip-blocks' to pragma 'optimize' [-Wpragmas]
 #pragma GCC optimize("-fcse-skip-blocks")
                                         ^
foo.cc:48:51: warning: bad option '-funsafe-loop-optimizations' to pragma 'optimize' [-Wpragmas]
 #pragma GCC optimize("-funsafe-loop-optimizations")
                                                   ^
foo.cc:63:22: warning: bad option '-fwhole-program' to attribute 'optimize' [-Wattributes]
 void add(int u, int v)
                      ^
foo.cc:63:22: warning: bad option '-fcse-skip-blocks' to attribute 'optimize' [-Wattributes]
foo.cc:63:22: warning: bad option '-funsafe-loop-optimizations' to attribute 'optimize' [-Wattributes]
foo.cc:76:16: warning: bad option '-fwhole-program' to attribute 'optimize' [-Wattributes]
 int dfs(int cur)
                ^
foo.cc:76:16: warning: bad option '-fcse-skip-blocks' to attribute 'optimize' [-Wattributes]
foo.cc:76:16: warning: bad option '-funsafe-loop-optimizations' to attribute 'optimize' [-Wattributes]
foo.cc:92:18: warning: bad option '-fwhole-program' to attribute 'optimize' [-Wattributes]
 void rdfs(int cur)
                  ^
foo.cc:92:18: warning: bad option '-fcse-skip-blocks' to attribute 'optimize' [-Wattributes]
foo.cc:92:18: warning: bad option '-funsafe-loop-optimizations' to attribute 'optimize' [-Wattributes]
foo.cc:99:10: warning: bad option '-fwhole-program' to attribute 'optimize' [-Wattributes]
 int main()
          ^
foo.cc:99:10: warning: bad option '-fcse-skip-blocks' to attribute 'optimize' [-Wattributes]
foo.cc:99:10: warning: bad option '-funsafe-loop-optimizations' to attribute 'optimize' [-Wattributes]
foo.cc: In function 'int main()':
foo.cc:101:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:103:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d", &k[i]);
         ~~~~~^~~~~~~~~~~~~
foo.cc:107:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &u, &v);
         ~~~~~^~~~~~~~~~~~~~~~~

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