Let `n_1`, `n_2`,.....`n_k` be the number of vertices respectively in K connected components of a
forest G,

then `n_1` - 1, `n_2`- 1,.....,`n_k` - 1  be the number of edges respectively in K  connected
components and

 `n_1` + `n_2` +..... + `n_k` = n (number of vertices in G) 

 Hence, number of edges in G = number of edges in K connected components

= (`n_1` - 1) + (`n_2` - 1`) +...... + (`n_k`) - 1  = n - k