foo.cc: In function 'int main()':
foo.cc:8:10: error: 'INT_MAX' was not declared in this scope
  int min=INT_MAX,k;
          ^~~~~~~
foo.cc:8:10: note: suggested alternative: 'INT8_MAX'
  int min=INT_MAX,k;
          ^~~~~~~
          INT8_MAX
foo.cc:13:4: error: 'k' was not declared in this scope
    k=n/a*b;
    ^
foo.cc:15:4: error: 'k' was not declared in this scope
    k=(n/a+1)*b;
    ^
foo.cc:16:6: error: 'k' was not declared in this scope
   if(k<min)min=k;
      ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。