def sum( x )
	a = 0
	x.length.times { |i|
		a += x[ i ]
	}
	return a
end

def sum2( x )
	a = 0
	x.length.times { |i|
		a += x[ i ] * x[ i ]
	}
	return a
end

def sum_xy( x , y )
	a = 0 
	x.length.times { |i|
		a += x[ i ] * y[ i ]
	}
	return a
end	

x = [ 7 , 6 , 4 , 2 , 5 ]
y = [ 24 , 20 , 14 , 8 ,12 ]

s_xy = sum_xy( x , y )
printf( "配列xとyの内積は%dです\n" , s_xy )