INDEX(array[,row, col, area])
INDEX gives a reference to a cell in the given array.The cell is pointed out by row and col, which count the rows and columns in the array.
Let us assume that the cells A1, A2, ..., A5 contain numbers 11.4, 17.3, 21.3, 25.9, and 40.1. Then INDEX(A1:A5,4,1,1) equals 25.9