#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef pair<ll,ll> P;
typedef modint1000000007 mint;
#define rep(i,a,b) for(ll i=a;i<b;i++)
#define rrep(i,a,b) for(ll i=a;i>=b;i--)
const ll inf=1e12;
ll p,q,r;
ll k;
ll a[10000];
ll t;
int main(void){
    cin.tie(0);
    ios::sync_with_stdio(0);
    cin>>p>>q>>r>>k;
    a[1]=p%10;
    a[2]=q%10;
    a[3]=r%10;
    rep(i,4,1005){
        a[i]=(a[i-1]+a[i-2]+a[i-3])%10;
        if(a[i]==a[3]&&a[i-1]==a[2]&&a[i-2]==a[1]){
            t=i-3;
            break;
        }
    }
    k%=t;
    ll ans=a[k];
    cout<<ans<<endl;
}