辗转相除法原理

例：

n1=60  n2=25

n1%n2=10

n1=25  n2=10

n1%n2=5

n1=10  n2=5

n1%n2=0

最大公约数就等 n2=5

int Division(int n1,int n2)
{
	if (n1 < n2){
		int temp = n1;
		n1 = n2;
		n2 = temp;
	}
	while (n1%n2 != 0){
		int temp = n1%n2;
		n1 = n2;
		n2 = temp;
	}
	return n2;
}