#include<stdio.h>
#include<math.h>
main()
{
int a,b,c,r,m,n,p;
scanf("%d%d%d",&a,&b.&c);
r=a%b;
while(r!=0)
{a=b;b=r;
r=a%b;}
m=b;
n=c%m;
while(n!=0)
{c=m;m=n;
n=c%m;}
printf("%d",m);
}

能详细说吗，我看不懂啊