foo.cc: In function 'pii dfs(int)':
foo.cc:27:11: warning: unused variable 'c1' [-Wunused-variable]
 int s1,s2,c1,c2;
           ^~
foo.cc:27:14: warning: unused variable 'c2' [-Wunused-variable]
 int s1,s2,c1,c2;
              ^~
foo.cc: In function 'int main()':
foo.cc:66:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n);
 ~~~~~^~~~~~~~~
foo.cc:70:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&price[i]);
 ~~~~~^~~~~~~~~~~~~~~~

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