local n, k = io.read("*n", "*n") local a = {} for i = 1, n do a[i] = io.read("*n") end if a[k] == 0 then print(0) else local left = k for i = k - 1, 1, -1 do if a[i] == 0 then break else left = i if a[i] == 1 then break end end end local right = k for i = k + 1, n do if a[i] == 0 then break else right = i if a[i] == 1 then break end end end local leftsum = 0LL for i = left, k - 1 do leftsum = leftsum + a[i] end local rightsum = 0LL for i = k + 1, right do rightsum = rightsum + a[i] end if a[k] == 1 then local ret = leftsum < rightsum and rightsum or leftsum ret = ret + a[k] local str = tostring(ret):gsub("LL", "") print(str) else local ret = a[k] + leftsum + rightsum local str = tostring(ret):gsub("LL", "") print(str) end end