// 放て！心に刻んだ夢を
// 未来さえ置き去りにして
// 限界など知らない　意味無い
// この能力が光散らす
// その先に遥かな想いを
#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ul unsigned ll
#define LL __int128_t
#define db double
#define DB long db
#define pii pair<int, int>
#define pil pair<int, ll>
#define fi first
#define se second
#define mkpr make_pair
#define vi vector<int>
#define vii vector<pii>
#define vil vector<pil>
#define eb emplace_back
#define all(c) (c).begin(), (c).end()
#define bit(x) (1 << (x))
#define bin(s, x) ((s) >> (x) & 1)
#define mem(a, x) memset(a, x, sizeof(a))
#define req(i, l, r) for (int i(l), i##End(r); i < i##End; i = -~i)
#define qer(i, r, l) for (int i(r), i##End(l); i > i##End; i = ~-i)
#define rep(i, l, r) for (int i(l), i##End(r); i <= i##End; i = -~i)
#define per(i, r, l) for (int i(r), i##End(l); i >= i##End; i = ~-i)

#ifdef JYR
#define errs(x) fputs(x "\n", stderr)
#define errm(x, ...) fprintf(stderr, x, ##__VA_ARGS__)
#else
#define errs(x) 0
#define errm(x, ...) 0
#endif

template<typename T, typename U> void chkmx(T &_a, U _b) { if (_a < _b) _a = _b; }
template<typename T, typename U> void chkmn(T &_a, U _b) { if (_a > _b) _a = _b; }
template<typename T> T sq(T x) { return x * x; }

bool Mbe;

// #define MC

#define N 300005
#define mod 998244353
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f

int n, m;
int a[N];
vi G[N], H[N << 2];
int dg[N << 2], ds[N << 2];
int qu[N << 2], lq, rq;
bool vs[N << 2];

void topo() {
    lq = 1, rq = 0;
    rep(u, 1, n) rep(i, 0, 1) {
        int x = u << 2 | a[u] << 1 | i;
        if (!dg[x]) qu[++rq] = x, ds[x] = 1;
    }
    while (lq <= rq) {
        int u = qu[lq++];
        for (auto v : H[u]) {
            chkmx(ds[v], ds[u] + 1);
            if (!--dg[v]) qu[++rq] = v;
        }
    }
}

void mslv() {
    scanf("%d%d", &n, &m);
    rep(i, 1, n) scanf("%d", a + i);
    rep(i, 1, m) {
        int u, v;
        scanf("%d%d", &u, &v);
        G[u].eb(v), G[v].eb(u);
    }
    rep(u, 1, n) rep(i, 0, 1) {
        int x = u << 2 | a[u] << 1 | i;
        for (auto v : G[u]) if (i == a[v]) rep(j, 0, 1) {
            int y = v << 2 | a[v] << 1 | j;
            if ((!a[u] && !i &&  j)
             || (!a[u] &&  i &&  j)
             || ( a[u] &&  i && !j)
             || ( a[u] && !i && !j)) H[x].eb(y), dg[y]++;
        }
    }
    if (topo(); rq != n << 1) {
        puts("infinity");
        return;
    }
    int ans[4] = {};
    rep(u, 1, n) rep(i, 0, 1) {
        int x = u << 2 | a[u] << 1 | i;
        chkmx(ans[x & 3], ds[x]);
    }
    printf("%d\n", *min_element(ans, ans + 4) + 1);
}

void sprw() {}

void mprw() {}

bool Med;

int main() {
    #ifdef JYR
    freopen("Test.in", "r", stdin);
    freopen("Test.out", "w", stdout);
    #endif
    mprw();
    #ifdef MC
    int _; scanf("%d", &_);
    while (_--) sprw(), mslv();
    #else
    mslv();
    #endif
    errm("%.3lfMB %.0lfms\n", abs(&Med - &Mbe) / 1048576., clock() * 1000. / CLOCKS_PER_SEC);
    return 0;
}