#include<iostream.h>

int cmmdc(int x, int y)
{ while(x!=y)
    if(x>y) x=x-y;
    else y=y-x;
  return x;
}

void main()
{ int a,b,c,d;
  cin>>a>>b>>c>>d;
  cout<<cmmdc(cmmdc(a,b),cmmdc(c,d));
}