#include <iostream>
#include <stdlib.h>
#include <time.h>

using namespace std;
int losuj()
{
    srand(time(0));
    int a;
    a=rand()%30000;
}

int nwd(int a,int b)
{
    int c;
    while(b != 0)
    {
        c=a % b;
        a = b;
        b = c;
    }
    return a;
}

int main()
{
    int y=0, y1=0, y2=1;

    int i=0;
    int sumanwd=0;



    while(y2!=0)
    {

        cin>>y1>>y2; //kiedys tu bedzie losowanie

        if(i<3)
        {
            if(y1==0 || y1==1 )
            {
                cin>>y1; //tutaj tez
            }

            if(y2==0 || y2==1)
            {
                cin>>y2; //i tu tez
            }
        }

        if(y2==1)
        {
            sumanwd=sumanwd+nwd(y,y1);
        }

        y=y1;
        y1=y2;

    }

cout<<sumanwd;

    return 0;
}