/in/foo.cc: In function 'int main()':
/in/foo.cc:16:23: warning: left operand of comma operator has no effect [-Wunused-value]
         for(int i=0;i,n;i++)
                       ^
/in/foo.cc:33:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for(int i=0;i<mark-1;i++)
     ^~~
/in/foo.cc:35:9: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
         if(b[mark*t-1]==0)cout<<endl;
         ^~