#include <bits/stdc++.h>
using namespace std;

long long mod = 998244353;
//入力が必ず-mod<a<modの時.
struct mint{
    long long v = 0;
    mint(){} mint(int a){v = a<0?a+mod:a;} mint(long long a){v = a<0?a+mod:a;}
    mint(unsigned long long a){v = a;}
    long long val(){return v;}
    void modu(){v %= mod;}
 
    mint repeat2mint(const long long a,long long b){
        mint ret = 1,p = a;
        while(b){
            if(b&1) ret *= p;
            p *= p; b >>= 1;
        }
        return ret;
    };
 
    mint &operator=(const mint &b) = default;
    mint operator-() const {return mint(0)-(*this);}
    mint operator+(const mint b){return mint(v)+=b;}
    mint operator-(const mint b){return mint(v)-=b;}
    mint operator*(const mint b){return mint(v)*=b;}
    mint operator/(const mint b){return mint(v)/=b;}
 
    mint operator+=(const mint b){
        v += b.v; if(v >= mod) v -= mod;
        return *this;
    }
    mint operator-=(const mint b){
        v -= b.v; if(v < 0) v += mod; 
        return *this;
    }   
    mint operator*=(const mint b){v = v*b.v%mod; return *this;}
    mint operator/=(mint b){
        if(b == 0) assert(false);
        int left = mod-2;
        while(left){if(left&1) *this *= b; b *= b; left >>= 1;}
        return *this;
    }
 
    mint operator++(int){*this += 1; return *this;}
    mint operator--(int){*this -= 1; return *this;}
    bool operator==(const mint b){return v == b.v;}
    bool operator!=(const mint b){return v != b.v;}
    bool operator>(const mint b){return v > b.v;}
    bool operator>=(const mint b){return v >= b.v;}
    bool operator<(const mint b){return v < b.v;}
    bool operator<=(const mint b){return v <= b.v;}
 
    mint pow(const long long x){return repeat2mint(v,x);}
    mint inv(){return mint(1)/v;}
};

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N,M; cin >> N >> M;
    string s; cin >> s;
    vector<vector<int>> Graph(N);
    for(int i=0; i<M; i++){
        int u,v; cin >> u >> v;
        u--; v--;
        Graph.at(u).push_back(v);
        Graph.at(v).push_back(u);
    }

    int ques = 0;
    for(auto c : s) ques += c=='?';

    mint div26 = mint(1)/26;

    vector<mint> dp(N),dp2(N);
    for(int i=0; i<N; i++){
        if(s.at(i) == 'a') dp.at(i) = 1;
        if(s.at(i) == '?') dp.at(i) = div26;
    }

    vector<vector<mint>> ok(N,vector<mint>(N));
    for(int pos=0; pos<N; pos++) if(dp.at(pos) > 0) for(auto to : Graph.at(pos)){
        if(s.at(to) == 'o') dp2.at(to) += dp.at(pos),ok.at(pos).at(to) = dp.at(pos);
        else if(s.at(to) == '?') dp2.at(to) += dp.at(pos)*div26,ok.at(pos).at(to) = dp.at(pos)*div26;
    }

    mint answer = 0;
    for(int pos=0; pos<N; pos++) for(auto to : Graph.at(pos)){
        if(s.at(to) == 'i') answer += dp2.at(pos);
        else if(s.at(to) == '?') answer += (dp2.at(pos)-ok.at(to).at(pos))*div26;
    }
    answer *= mint(26).pow(ques);
    cout << answer.v << endl;
}