#include <stdio.h>
#include <string.h>
using namespace std;

#define BASE 1000000000
#define FORMAT "%09d"
#define NRC 9
#define NMAX 1010
#define CMAX 70
#define LL long long

int N, D;

int A[CMAX];
int B[CMAX];

int aux[CMAX];
int aux1[CMAX];

char s[CMAX];

int ant[NMAX][CMAX];
int cur[NMAX][CMAX];

int comb[NMAX][CMAX];

inline int MAX(int a, int b) { return (a > b) ? a : b; }

void get(int a[], char s[])
{
	int n = strlen(s), i, j, q;
	a[0] = 0;

	for (i = n - 1; i >= 0; i -= NRC) {
		for (j = MAX(0, i - NRC + 1), q = 0; j <= i; j++) q = q * 10 + s[j] - '0';
		a[++a[0]] = q;
	}
}

void print_nr(int a[])
{
	int i;

	printf("%d", a[a[0]]);

	for (i = a[0] - 1; i >= 1; i--) 
		printf(FORMAT, a[i]);

	printf("\n");
}

void add(int a[], int b[])
{
	int i, t = 0;

	for (i = 1; i <= a[0] || i <= b[0] || t; i++, t /= BASE)
		a[i] = (t += a[i] + b[i]) % BASE;

	a[0] = i - 1;
}

int C[CMAX];

void mul(int A[], int B[])
{
	      int i, j;
		  LL t;
	       memset(C, 0, sizeof(C));
	     for (i = 1; i <= A[0]; i++)
	       {
	             for (t=0, j=1; j <= B[0] || t; j++, t/=BASE)
	                 C[i+j-1]=(t+=C[i+j-1]+(LL)A[i]*B[j])%BASE;
	          if (i + j - 2 > C[0]) C[0] = i + j - 2;
		 }
       memcpy(A, C, sizeof(C));
}

int mai_mic(int a[], int b[])
{
	if (a[0] < b[0]) return 1;
	if (a[0] > b[0]) return 0;

	for (int i = a[0]; i >= 1; i--) {
		if (a[i] < b[i]) return 1;
		if (a[i] > b[i]) return 0;
	}

return 1;
}

void scad(int a[], int b[])
{
	int i;

	for (i = 1; i <= a[0]; i++) {
		a[i] -= b[i];
		if (a[i] < 0) a[i] += BASE, a[i+1]--;
	}

	while (a[0] && !a[a[0]]) a[0]--;
}

int main()
{
	int i, j;

	freopen("bile2.in", "r", stdin);
	freopen("bile2.out", "w", stdout);

	scanf("%d %d", &N, &D);

	scanf("%s", s);
	get(A, s);
	scanf("%s", s);
	get(B, s);

	ant[0][0] = 1; ant[0][1] = 1;
	int lim;
	for (i = 1; i <= N; i++) {
		cur[0][0] = 1; cur[0][1] = 1;

		lim = i / 2 + 1;
		for (j = 1; j <= i; j++) {
			if (j <= lim) {
				memcpy(cur[j], ant[j - 1], sizeof(cur[j]));
				add(cur[j], ant[j]);
			} else memcpy(cur[j], cur[i - j + 1], sizeof(cur[j]));
		}

		memcpy(ant, cur, sizeof(cur));
	}

	memcpy(comb, cur, sizeof(cur));

	memset(ant, 0, sizeof(ant));
	memset(cur, 0, sizeof(cur));
	for (i = 1; i <= N; i++) { // aleg i
		for (j = 1; j <= N; j++) {
			if (i == 1) {
				cur[j][0] = 1; cur[j][1] = 1;
				add(cur[j], cur[j-1]);
			} else {
				memcpy(cur[j], cur[j-1], sizeof(cur[j]));
				if (j - D - 1 > 0) add(cur[j], ant[j - D - 1]);
			}
		}

		memcpy(aux, comb[i], sizeof(aux));
		memcpy(aux1, cur[N], sizeof(aux));
		scad(aux, aux1);
		
		mul(aux, B);

		memcpy(aux1, comb[i], sizeof(aux1));
		mul(aux1, A);

		
		if (mai_mic(aux1, aux)) break;

		memcpy(ant, cur, sizeof(ant));
	}

	printf("%d\n", i);

return 0;
}