foo.cc: In function 'int main()':
foo.cc:111:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j=0; j<a_s[i].size(); j++)
                  ~^~~~~~~~~~~~~~
foo.cc:125:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j=0; j<b_s[i].size(); j++)
                  ~^~~~~~~~~~~~~~
foo.cc:141:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i=0; i<p_1_s.size(); i++)
                  ~^~~~~~~~~~~~~
foo.cc:146:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i=0; i<p_2_s.size(); i++)
                   ~^~~~~~~~~~~~~
foo.cc:110:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d%s",&a_x[i],&a_y[i],&(a_s[i][0]));
    ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:124:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d%s",&b_x[i],&b_y[i],&(b_s[i][0]));
    ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:145:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s%d",&(p_2_s[0]),&p);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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