#include <stdio.h>
#include <string.h>
#include <stdlib.h>

const char * infile = "ctriangle.inp";
const char *outfile = "ctriangle.out";

int F;
long long k, n;

long long t0ll(char *s)
{
	long long q = 0;
	for (unsigned i = 0; i < strlen(s); i++)
		q = q * 10LL + (long long) (s[i]-'0');
	return q;
}

int aa[1000000];
int bb[1000000];
int ans;


void solve(void)
{
	int *a = aa;
	int *b = bb;
	for (long long i = 1LL; i <= k; i++) {
		int sum = 0;
		for (int j = 0; j<=i; j++) {
			if (j == 0) b[j] = 1; else
				if (j == i) b[j] = i * F; else
					b[j] = a[j-1] + a[j];
			sum += b[j];
		}
		if (k == i) {
			ans = sum % 10;
			break;
		}
		int *t  = a;
		a = b;
		b = t;
	}
	
}

long long sum(long long n)
{
	int ans = 0;
	for (int i = 1; i <= n; i++)
		ans += i;
	return ans;
//	return (n*(n+1LL))/2LL;
}

void solve2(void)
{
//	ans = (int) ((sum(k-1) + sum(k)*F) % 10LL);
	
}

int main(void)
{
	FILE *f = fopen(infile, "rt");
	FILE *fout = fopen(outfile, "wt");
	char ss[1000], ss1[1000];
	while (3 == fscanf(f, "%s%s%d", ss, ss1, &F)) {
		memset(aa, 0,sizeof(aa));
//		printf("%s %s %d\n", ss, ss1, f);		fflush(stdout);
		n = t0ll(ss);
		k = t0ll(ss1);
		k--;
		ans = 0; 
		if (k) {
			if (k < 2000)
				solve();
			else
				solve2();
		}
		fprintf(fout, "%d\n", ans);fflush(stdout);
	}
	fclose(f);
	fclose(fout);
//	system("pause");
	return 0;
}