读不懂这里的if while的内容 大佬可以解答下吗 万分感谢

#include <stdio.h>

int main() {
    int p, r, m, n, temp;
    printf("请输入两个正数:\n");
    scanf_s("%d,%d",&m,&n);
    // 假设输入的是10,5 则m = 10,n = 5;
    if (n < m) //5<10 成立
    {
        temp = n;
        //把n的值赋给temp,此时temp=5,n=5,m=10
        n = m;
        //把m的值赋给n,此时temp=5,n=10,m=10
        m = temp;
        //把temp的值赋给m,此时temp=5,n=10,m=5
        //temp相当于工具人,把m与n的值互换
    }// 确保n为大值
    p = n * m;
    // p = 5 * 10 = 50; n = 10; m = 5;
        while (m != 0) //m!=0 成立
        {
            r = n % m;
            //r = 10 % 5 = 0
            n = m;
            //把m的值赋给n，此时r = 0, n = 5, m = 5;
            m=r;
            //把r的值赋给m,此时 r = 0; m = 0; n = 5; p = 50;
        }// 运算
        printf("它们的最大公约数:%d",n);
        printf("它们的最小公倍数为:%d\n",p/n);
   
    return 0;
}