#include <bits/stdc++.h>

using namespace std;

#define DEBUG 0
#define TIME clock() / 1.0 / CLOCKS_PER_SEC

const int maxN = (int)3e5 + 17;

int n, m;
int a[maxN];
int used[maxN];
vector <int> dd;
int dp[maxN][26];
vector <int> g[maxN];

void TopSort(int v) {
    used[v] = 1;
    //cout << "- >" <<  v + 1 << ' ';
    for(const auto to : g[v]) {
        if(used[to] == 1) {
            cout << -1 << '\n';
            exit(0);
        } else if(used[to] == 0) {
            TopSort(to);
        }
    }
    used[v] = 2;
    dd.push_back(v);
}

void dfs(int v, int colour) {
    used[v] = 1;
    if(g[v].size() == 0) {
        dp[v][colour] = (colour == a[v]);
    }
    for(const auto to : g[v]) {
        if(!used[to]) {
            dfs(to, colour);
        }
        dp[v][colour] = max(dp[v][colour], dp[to][colour] + (colour == a[to]));
    }
}

int solve(int v) {
    int ret = 0;
    for(int i = 0; i < dd.size(); ++i) {
        if(!used[dd[i]])
            dfs(dd[i], v);
    }
    fill(used, used + maxN, 0);
    for(int i = 0; i < n; ++i) {
        ret = max(ret, dp[i][v]);
    }
    return ret;
}

signed main()
{
    #if DEBUG
        freopen("input.txt", "r", stdin);
        freopen("output.txt" , "w", stdout);
    #endif

    cin >> n >> m;
    for(int i = 0; i < n; ++i) {
        char x; cin >> x;
        a[i] = x - 'a';
    }
    for(int i = 0; i < m; ++i) {
        int x, y;
        cin >> x >> y;
        g[x - 1].push_back(y - 1);
    }
    for(int i = 0; i < n; ++i) {
        if(!used[i])
            TopSort(i);
    }
    //reverse(dd.begin(), dd.end());
    fill(used, used + maxN, 0);
    for(const auto i : dd){
        cout << i + 1 << ' ';
    }
    cout << endl;

    int ans = 0;
    for(int i = 'a'; i <= 'z'; ++i){
        ans = max(ans, solve(i - 'a'));
    }

    cout << ans << '\n';

    return 0;
}