/in/foo.cc:3:10: error: #include expects "FILENAME" or <FILENAME>
 #include n 20
          ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:7:8: error: 'n' was not declared in this scope
  int a[n][n],i,j,k,N,max,min,index,num=0;
        ^
/in/foo.cc:13:9: error: 'a' was not declared in this scope
    cin>>a[i][j];
         ^
/in/foo.cc:21:7: error: 'a' was not declared in this scope
    if(a[i][j]>a[i][index])
       ^
/in/foo.cc:28:7: error: 'a' was not declared in this scope
    if(a[i][k]==a[i][index])
       ^
/in/foo.cc:7:22: warning: unused variable 'max' [-Wunused-variable]
  int a[n][n],i,j,k,N,max,min,index,num=0;
                      ^~~