i n 1 : a " - w{pX " , b " - w{pY " 
 
 i n 1 : c " - vhpX " , d " - vhpY " 
 
 o u t : i " - " , j " - eMO҉" 
 
 o u t : w " - eMO҉^Ry" 
 
 p o l ( c - a , d - b ) 
 
 j < 0 = > j = j + 3 6 0 
 
 w = d m s ( j ) 