Divide 7, 10, 12, 21, 22, 35, 48, 85, 91, 99 into several groups. It is required that the greatest common factor of any two numbers in each group is 1, so how many groups should they be divided into?
将7，10，12，21，22，35，48，85，91，99分成若干组，要求每一组中任意两个数的最大公因数是1，那么至少分成多少组．
<result>4</result>