foo.cc:29:11: error: redefinition of 'const int maxn'
 const int maxn = 2010;
           ^~~~
foo.cc:5:11: note: 'const int maxn' previously defined here
 const int maxn = 2010;
           ^~~~
foo.cc:30:18: error: redefinition of 'int dp [2010][2010]'
 int dp[maxn][maxn];
                  ^
foo.cc:6:5: note: 'int dp [2010][2010]' previously declared here
 int dp[maxn][maxn];
     ^~
foo.cc: In function 'int main()':
foo.cc:32:5: error: redefinition of 'int main()'
 int main() {
     ^~~~
foo.cc:8:5: note: 'int main()' previously defined here
 int main() {
     ^~~~

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