foo.cc: In function 'int main()':
foo.cc:84:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  freopen("river6.in","r",stdin);
  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
foo.cc:86:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld%lld",&n,&m);
  ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:88:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%s",c[i]+1);
   ~~~~~^~~~~~~~~~~~~
foo.cc:125:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld%lld",&x,&y);
   ~~~~~^~~~~~~~~~~~~~~~~~

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