text: if sum is seen before , we found two pairs
code: if ( s . ContainsKey ( sum ) ) { Console . Write ( " ( " + s [ sum ] . first + " , ▁ " + s [ sum ] . second + " ) ▁ and ▁ ( " + x + " , ▁ " + y + " ) " + " STRNEWLINE " ) ; } else