foo.cc: In function 'int main()':
foo.cc:31:16: warning: statement has no effect [-Wunused-value]
   31 |       b[i-1][j]=='R';
      |       ~~~~~~~~~^~~~~
foo.cc:33:16: warning: statement has no effect [-Wunused-value]
   33 |       b[i+1][j]=='R';
      |       ~~~~~~~~~^~~~~
foo.cc:35:16: warning: statement has no effect [-Wunused-value]
   35 |       b[i][j-1]=='R';
      |       ~~~~~~~~~^~~~~
foo.cc:37:16: warning: statement has no effect [-Wunused-value]
   37 |       b[i][j+1]=='R';
      |       ~~~~~~~~~^~~~~
foo.cc:42:16: warning: statement has no effect [-Wunused-value]
   42 |       b[i-1][j]=='S';
      |       ~~~~~~~~~^~~~~
foo.cc:44:16: warning: statement has no effect [-Wunused-value]
   44 |       b[i+1][j]=='S';
      |       ~~~~~~~~~^~~~~
foo.cc:46:16: warning: statement has no effect [-Wunused-value]
   46 |       b[i][j-1]=='S';
      |       ~~~~~~~~~^~~~~
foo.cc:48:16: warning: statement has no effect [-Wunused-value]
   48 |       b[i][j+1]=='S';
      |       ~~~~~~~~~^~~~~
foo.cc:53:16: warning: statement has no effect [-Wunused-value]
   53 |       b[i-1][j]=='P';
      |       ~~~~~~~~~^~~~~
foo.cc:55:16: warning: statement has no effect [-Wunused-value]
   55 |       b[i+1][j]=='P';
      |       ~~~~~~~~~^~~~~
foo.cc:57:16: warning: statement has no effect [-Wunused-value]
   57 |       b[i][j-1]=='P';
      |       ~~~~~~~~~^~~~~
foo.cc:59:16: warning: statement has no effect [-Wunused-value]
   59 |       b[i][j+1]=='P';
      |       ~~~~~~~~~^~~~~

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