This square square dancing at least 102 people, 7 people 7 people land number of the remaining 4 people = 7 people 7 people land number of less than 3 people, 7 people 7 people and 5 people 5 people are worse than three people, and 3 people 3 people land number is exactly the same, are three. 7,5,3 of the smallest common multiple of 105, and then 105-3 = 102 (people)
Checking: 102 ÷ 7 = 14 (group) ......4 (people), 102 ÷ 5 = 20 (groups) ......2 (people), if the number 21 groups, then 21 × 5-102 = 3 (people), 102 ÷ 3 = 34 (groups), there is no remainder. So 102 is correct.