/in/foo.cc:3:13: error: expected unqualified-id before 'int'
 int n,k,x,s,int a[13]; 
             ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:8:2: error: expected ',' or ';' before 'if'
  if(n%4==&&n%100!=0||n%400==0)
  ^~
/in/foo.cc:12:9: error: no match for 'operator+=' (operand types are 'std::basic_ostream<char>' and 'int')
  cout<<s+=x;
  ~~~~~~~^~~