#include <stdio.h>

#define N_MAX 100
#define M_MAX 5000



typedef struct Edge {
	struct Edge *next;
	int v;
	unsigned int label;
} edge;

void chmin(int* a, int b)
{
	if (*a > b) *a = b;
}



#define MT_N 624
#define MT_M 397
#define MT_MATRIX_A 0x9908b0dfUL
#define MT_UPPER_MASK 0x80000000UL
#define MT_LOWER_MASK 0x7fffffffUL

static unsigned int mt[MT_N];
static int mti = MT_N + 1;

void init_genrand(unsigned int s)
{
    mt[0] = s & 0xffffffffUL;
    for (mti = 1; mti < MT_N; mti++) {
        mt[mti] = (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 
        mt[mti] &= 0xffffffffUL;
    }
}

unsigned int genrand()
{
    unsigned int y;
    static unsigned int mag01[2] = {0x0UL, MT_MATRIX_A};

    if (mti >= MT_N) {
        int kk;
        if (mti == MT_N + 1) init_genrand(5489UL);
		
        for (kk = 0; kk < MT_N - MT_M; kk++) {
            y = (mt[kk] & MT_UPPER_MASK) | (mt[kk+1] & MT_LOWER_MASK);
            mt[kk] = mt[kk+MT_M] ^ (y >> 1) ^ mag01[y&0x1UL];
        }
        for (; kk < MT_N - 1; kk++) {
            y = (mt[kk] & MT_UPPER_MASK) | (mt[kk+1] & MT_LOWER_MASK);
            mt[kk] = mt[kk+(MT_M-MT_N)] ^ (y >> 1) ^ mag01[y&0x1UL];
        }
        y = (mt[MT_N-1] & MT_UPPER_MASK) | (mt[0] & MT_LOWER_MASK);
        mt[MT_N-1] = mt[MT_M-1] ^ (y >> 1) ^ mag01[y&0x1UL];

        mti = 0;
    }
  
    y = mt[mti++];

    y ^= (y >> 11);
    y ^= (y << 7) & 0x9d2c5680UL;
    y ^= (y << 15) & 0xefc60000UL;
    y ^= (y >> 18);

    return y;
}



#define POWX 3 // 3 -> 2^8, 4 -> 2^16, 5 -> 2^32
const unsigned int powd[5] = {2, 4, 16, 256, 65536}, powe[5] = {1, 2, 4, 8, 16};

// Multiplication on a finite field of size 2^32 with XOR addition
unsigned int nim_product(unsigned int A, unsigned int B)
{
	if (A > B) return nim_product(B, A);
	else if (A <= 1) return A * B;
	
	static unsigned int memo[256][256] = {};
	if (B < 256 && memo[A][B] != 0) return memo[A][B];
	
	int i;
	for (i = 0; i < POWX; i++) {
		if (B == powd[i]) {
			if (A == powd[i]) return (B >> 1) * 3;
			else return A * B;
		}
	}

	unsigned int a[2], b[2], ans[2][2];
	for (i = POWX - 1; i >= 0; i--) if (B > powd[i]) break;
	a[1] = A & (powd[i] - 1);
	a[0] = (A ^ a[1]) >> powe[i];
	b[1] = B & (powd[i] - 1);
	b[0] = (B ^ b[1]) >> powe[i];
	ans[0][0] = nim_product(a[0], b[0]);
	ans[0][1] = nim_product(a[0], b[1]);
	ans[1][0] = nim_product(a[1], b[0]);
	ans[1][1] = nim_product(a[1], b[1]);
	if (B < 256) {
		memo[A][B] = (ans[0][0] ^ ans[0][1] ^ ans[1][0]) * powd[i] ^ nim_product(ans[0][0], powd[i] >> 1) ^ ans[1][1];
		return memo[A][B];
	} else return (ans[0][0] ^ ans[0][1] ^ ans[1][0]) * powd[i] ^ nim_product(ans[0][0], powd[i] >> 1) ^ ans[1][1];
}



// Solution example (O(N^4) time by skipping terminals)
int solve4_3(int N, int M, int X, int Y, int Z, int A[], int B[])
{
	static int i, u, w, adj_mat[N_MAX + 1][N_MAX + 1];
	static edge *adj[N_MAX + 1], e[M_MAX * 2], *p, *pp;
	for (u = 1; u <= N; u++) for (w = u + 1; w <= N; w++) adj_mat[u][w] = 0;
	for (i = 1; i <= M; i++) {
		u = A[i];
		w = B[i];
		adj_mat[u][w] = 1;
	}
	for (u = 1; u <= N; u++) adj[u] = NULL;
	for (u = 1, i = 0; u <= N; u++) {
		for (w = u + 1; w <= N; w++) {
			if (adj_mat[u][w] != 0) continue;
			e[i].v = w;
			e[i].label = genrand() % (powd[POWX] - 1) + 1;
			e[i].next = adj[u];
			adj[u] = &(e[i++]);
			e[i].v = u;
			e[i].label = e[i-1].label;
			e[i].next = adj[w];
			adj[w] = &(e[i++]);
		}
	}
	
	static edge *d_adj[3][N_MAX + 1], f[N_MAX * N_MAX * 2];
	for (u = 1; u <= N; u++) {
		d_adj[1][u] = NULL;
		d_adj[2][u] = NULL;
	}
	for (p = adj[Y], i = 0; p != NULL; p = p->next) {
		u = p->v;
		for (pp = p->next; pp != NULL; pp = pp->next) {
			w = pp->v;
			f[i].v = w;
			f[i].label = nim_product(p->label, pp->label);
			f[i].next = d_adj[1][u];
			d_adj[1][u] = &(f[i++]);
			f[i].v = u;
			f[i].label = f[i-1].label;
			f[i].next = d_adj[1][w];
			d_adj[1][w] = &(f[i++]);
		}
	}
	for (p = adj[Z]; p != NULL; p = p->next) {
		u = p->v;
		for (pp = p->next; pp != NULL; pp = pp->next) {
			w = pp->v;
			f[i].v = w;
			f[i].label = nim_product(p->label, pp->label);
			f[i].next = d_adj[2][u];
			d_adj[2][u] = &(f[i++]);
			f[i].v = u;
			f[i].label = f[i-1].label;
			f[i].next = d_adj[2][w];
			d_adj[2][w] = &(f[i++]);
		}
	}
	
	static int k, kk, l, x, y, z;
	static unsigned int dp[N_MAX + 1][4][N_MAX + 1][N_MAX + 1], tmp;
	for (l = 1; l <= N; l++) {
		for (k = 0; k < 4; k++) {
			for (p = adj[X]; p != NULL; p = p->next) {
				for (u = 1; u <= N; u++) dp[l][k][p->v][u] = 0;
			}
		}
	}
	for (p = adj[X]; p != NULL; p = p->next) {
		u = p->v;
		dp[1][0][u][u] = p->label;
	}
	for (l = 1; l <= N; l++) {
		for (p = adj[X]; p != NULL; p = p->next) {
			for (pp = p->next; pp != NULL; pp = pp->next) if (dp[l][3][p->v][pp->v] != 0) return l + 1;
		}
		if (l == N) return -1;
		
		for (k = 0; k < 4; k++) {
			for (p = adj[X]; p != NULL; p = p->next) {
				w = p->v;
				for (y = 1; y <= N; y++) {
					if (y == X || y == Y || y == Z) continue;
					tmp = dp[l][k][w][y];
					for (pp = adj[y]; pp != NULL; pp = pp->next) {
						z = pp->v;
						dp[l+1][k][w][z] ^= nim_product(tmp, pp->label);
					}
					if (l == N - 1) continue;
					if ((k & 1) == 0) {
						for (pp = d_adj[1][y]; pp != NULL; pp = pp->next) {
							z = pp->v;
							dp[l+2][k|1][w][z] ^= nim_product(tmp, pp->label);
						}
					}
					if ((k & 2) == 0) {
						for (pp = d_adj[2][y]; pp != NULL; pp = pp->next) {
							z = pp->v;
							dp[l+2][k|2][w][z] ^= nim_product(tmp, pp->label);
						}
					}
				}
			}
		}
	}
}



int main()
{
	int i, N, M, X, Y, Z, A[M_MAX + 1], B[M_MAX + 1], ans[2];
	scanf("%d %d", &N, &M);
	scanf("%d %d %d", &X, &Y, &Z);
	for (i = 1; i <= M; i++) scanf("%d %d", &(A[i]), &(B[i]));
	ans[0] = solve4_3(N, M, X, Y, Z, A, B);
	// ans[1] = solve4_3(N, M, X, Y, Z, A, B);
	// chmin(&(ans[0]), ans[1]);
	printf("%d\n", (ans[0] > N)? -1: ans[0]);
	fflush(stdout);
	return 0;
}