foo.cc: In function 'std::vector<int> mul(std::vector<int>, int)':
foo.cc:49:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); i ++ )
                     ~~^~~~~~~~~~
foo.cc: In function 'void solve()':
foo.cc:86:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for (int i = 0; i < cnt; i ++ )
     ^~~
foo.cc:89:2: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  ll ans=0;
  ^~

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