Driver function .
M = [ [ 1 , 3 , 5 , 3 ] , [ 0 , 4 , 6 , 2 ] , [ 0 , 0 , 2 , 5 ] , [ 0 , 0 , 0 , 6 ] ] NEW_LINE if isuppertriangular ( M ) : NEW_LINE INDENT print ( " Yes " ) NEW_LINE DEDENT else : NEW_LINE INDENT print ( " No " ) NEW_LINE DEDENT