for (i = 1; i <= n; i++) {
if (i == OTU1 || i == OTU2) continue;
x = D[give_index(i, OTU1, n)]; /* dist between OTU1 and i */
y = D[give_index(i, OTU2, n)]; /* dist between OTU2 and i */
for (i = 1; i <= n; i++) {
if (i == OTU1 || i == OTU2) continue;
x = D[give_index(i, OTU1, n)]; /* dist between OTU1 and i */
y = D[give_index(i, OTU2, n)]; /* dist between OTU2 and i */