#include<cstdio>
#include<vector>
using namespace std;
using ull = unsigned long long;

int main(){
    unsigned p, q, r;
    ull K;
    scanf("%u %u %u %llu", &p, &q, &r, &K);
    p %= 10, q %= 10, r %= 10;
    vector<unsigned> a(1000, 0);
    unsigned status = p*100 + q*10 + r, now, one_before, two_before, sum, count = 3;
    a[(10 + (q<<1) - r) %10*100 + (20 + r - p - q)%10*10 + p] = 1;
    a[(20 + r - p - q)%10*100 + p*10 + q] = 2;
    do{
        sum = (p + q + r)%10;
        p = q, q = r, r = sum;
        a[status] = count++;
        status = status%100*10 + r;
    }while(!a[status] && count < K);
    if(count == K){
        printf("%u\n", r);
        return 0;
    }
    K = (K - count)%(count - a[status]);
    for (unsigned i = 0; i < K; i++)
    {
        sum = (p + q + r)%10;
        p = q, q = r, r = sum;
    }
    printf("%u\n", r);
	return 0;
}