#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
#endif
using ll=long long;
using ull=unsigned long long;
using P=pair<ll,ll>;
template<typename T>using minque=priority_queue<T,vector<T>,greater<T>>;
template<typename T>bool chmax(T &a,const T &b){return (a<b?(a=b,true):false);}
template<typename T>bool chmin(T &a,const T &b){return (a>b?(a=b,true):false);}
template<typename T1,typename T2>istream &operator>>(istream &is,pair<T1,T2>&p){is>>p.first>>p.second;return is;}
template<typename T1,typename T2,typename T3>istream &operator>>(istream &is,tuple<T1,T2,T3>&a){is>>std::get<0>(a)>>std::get<1>(a)>>std::get<2>(a);return is;}
template<typename T>istream &operator>>(istream &is,vector<T> &a){for(auto &i:a)is>>i;return is;}
template<typename T1,typename T2>void operator++(pair<T1,T2>&a,int n){a.first++,a.second++;}
template<typename T1,typename T2>void operator--(pair<T1,T2>&a,int n){a.first--,a.second--;}
template<typename T>void operator++(vector<T>&a,int n){for(auto &i:a)i++;}
template<typename T>void operator--(vector<T>&a,int n){for(auto &i:a)i--;}
#define overload3(_1,_2,_3,name,...) name
#define rep1(i,n) for(int i=0;i<(int)(n);i++)
#define rep2(i,l,r) for(int i=(int)(l);i<(int)(r);i++)
#define rep(...) overload3(__VA_ARGS__,rep2,rep1)(__VA_ARGS__)
#define reps(i,l,r) rep2(i,l,r)
#define all(x) x.begin(),x.end()
#define pcnt(x) __builtin_popcountll(x)
#define fin(x) return cout<<(x)<<'\n',static_cast<void>(0)
#define yn(x) cout<<((x)?"Yes\n":"No\n")
#define uniq(x) sort(all(x)),x.erase(unique(all(x)),x.end())
ll myceil(ll a,ll b){return (a+b-1)/b;}
template<typename T,size_t n,size_t id=0>
auto vec(const int (&d)[n],const T &init=T()){
  if constexpr (id<n)return vector(d[id],vec<T,n,id+1>(d,init));
  else return init;
}
#ifdef LOCAL
#include<debug.h>
#else
#define debug(...) static_cast<void>(0)
#define debugg(...) static_cast<void>(0)
template<typename T1,typename T2>ostream &operator<<(ostream &os,const pair<T1,T2>&p){os<<p.first<<' '<<p.second;return os;}
#endif
struct Timer{
  clock_t start;
  Timer(){
    start=clock();
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout<<fixed<<setprecision(16);
  }
  inline double now(){return (double)(clock()-start)/1000;}
  #ifdef LOCAL
  ~Timer(){
    cerr<<"time:";
    cerr<<now();
    cerr<<"ms\n";
  }
  #endif
}timer;
void SOLVE();
int main(){
  int testcase=1;
  //cin>>testcase;
  for(int i=0;i<testcase;i++){
    SOLVE();
  }
}
#include<type_traits>
#include<optional>
template<typename T>
constexpr std::enable_if_t<std::numeric_limits<T>::digits<=32,int>msb(T n){return n==0?-1:31-__builtin_clz(n);}
template<typename T>
constexpr std::enable_if_t<(std::numeric_limits<T>::digits>32),int>msb(T n){return n==0?-1:63-__builtin_clzll(n);}

template<typename T>
constexpr std::enable_if_t<std::numeric_limits<T>::digits<=32,int>lsb(T n){return n==0?-1:__builtin_ctz(n);}
template<typename T>
constexpr std::enable_if_t<(std::numeric_limits<T>::digits>32),int>lsb(T n){return n==0?-1:__builtin_ctzll(n);}

template<typename T>
constexpr std::enable_if_t<std::is_integral_v<T>,T>floor_pow2(T n){return n==0?0:T(1)<<msb(n);}

template<typename T>
constexpr std::enable_if_t<std::is_integral_v<T>,T>ceil_pow2(T n){return n<=1?1:T(1)<<(msb(n-1)+1);}
constexpr unsigned long long binary_gcd(unsigned long long a,unsigned long long b){
  if(a==0||b==0||a==b)return a<b?b:a;
  int n=lsb(a),m=lsb(b);
  while(a!=b){
    if(a>b)a=(a-b)>>lsb(a-b);
    else b=(b-a)>>lsb(b-a);
  }
  return a<<(n<m?n:m);
}
struct BarrettReduction{
private:
  using i64=long long;
  using u64=unsigned long long;
  using u32=unsigned int;
  using u128=__uint128_t;
  u32 m;
  u64 im;
public:
  BarrettReduction():m(0),im(0){}
  BarrettReduction(u32 n):m(n),im(u64(-1)/n+1){}
  inline i64 quo(u64 x)const{
    if(m==1)return x;
    u64 y=u64((u128(x)*im)>>64);
    u32 r=x-y*m;
    return m<=r?y-1:y;
  }
  inline u32 rem(u64 x)const{
    if(m==1)return 0;
    u64 y=u64((u128(x)*im)>>64);
    u32 r=x-y*m;
    return m<=r?r+m:r;
  }
  inline std::pair<u64,u32>quo_rem(u64 x)const{
    if(m==0)return std::make_pair(x,0);
    u64 y=u64((u128(x)*im)>>64);
    u32 r=x-y*m;
    return m<=r?std::make_pair(y-1,r+m):std::make_pair(y,r);
  }
  inline u32 pow(u32 a,u64 p)const{
    u32 res=m!=1;
    while(p){
      if(p&1)res=rem(u64(res)*a);
      a=rem(u64(a)*a);
      p>>=1;
    }
    return res;
  }
};
namespace prime_impl{
constexpr int table_size=1<<16;
bool table[table_size];
struct prime_table_init{
  prime_table_init(){
    table[0]=table[1]=true;
    for(int i=2;i<table_size;i++)if(!table[i]){
      for(int j=i*2;j<table_size;j+=i)table[j]=true;
    }
  }
}dummy;
}
bool isprime(unsigned long long n)noexcept{
  if(n<prime_impl::table_size)return !prime_impl::table[n];
  if(n%2==0)return false;
  if(n<(1ull<<31)){
    BarrettReduction br(n);
    unsigned long long d=n-1;
    while(!(d&1))d>>=1;
    for(unsigned long long base:{2,7,61}){
      unsigned long long t=d;
      unsigned long long y=1;
      while(t>0){
        if(t&1)y=br.rem(y*base);
        base=br.rem(base*base);
        t>>=1;
      }
      t=d;
      while(t!=n-1&&y!=1&&y!=n-1){
        y=br.rem(y*y);
        t<<=1;
      }
      if(y!=n-1&&t%2==0)return false;
    }
    return true;
  }
  unsigned long long d=n-1;
  int s=0;
  while(!(d&1))d>>=1,s++;
  int q=63;
  while(!(d>>q))q--;
  unsigned long long r=n;
  for(int i=0;i<5;i++)r*=2-r*n;
  auto redc=[&r,&n](__uint128_t x)->unsigned long long {
    x=(x+__uint128_t((unsigned long long)x*-r)*n)>>64;
    return x>=n?x-n:x;
  };
  __uint128_t r2=-__uint128_t(n)%n;
  unsigned long long one=redc(r2);
  for(unsigned long long base:{2,325,9375,28178,450775,9780504,1795265022}){
    if(base%n==0)continue;
    unsigned long long a=base=redc((base%n)*r2);
    for(int i=q-1;i>=0;i--){
      a=redc(__uint128_t(a)*a);
      if(d>>i&1)a=redc(__uint128_t(a)*base);
    }
    if(a==one)continue;
    for(int i=1;a!=n-one;i++){
      if(i>=s)return false;
      a=redc(__uint128_t(a)*a);
    }
  }
  return true;
}
std::vector<unsigned long long>factorize(unsigned long long n)noexcept{
  std::vector<unsigned long long>ret;
  auto div=[](unsigned long long x)noexcept->unsigned long long {
    unsigned long long r=x;
    for(int i=0;i<5;i++)r*=2-r*x;
    unsigned long long r2=-__uint128_t(x)%x;
    auto redc=[&r,&x](__uint128_t t)->unsigned long long {
      t=(t+__uint128_t((unsigned long long)t*-r)*x)>>64;
      return t>=x?t-x:t;
    };
    unsigned long long a=0,b=0;
    const unsigned long long one=redc(r2);
    unsigned long long e=one;
    int m=1ll<<((63-__builtin_clzll(x))>>3);
    while(true){
      unsigned long long ca=a,cb=b;
      unsigned long long sk=one;
      for(int i=0;i<m;i++){
        a=redc(__uint128_t(a)*a+e);
        b=redc(__uint128_t(b)*b+e);
        b=redc(__uint128_t(b)*b+e);
        unsigned long long c=redc(a),d=redc(b);
        sk=redc(__uint128_t(sk)*(c>d?c-d:d-c));
      }
      unsigned long long g=binary_gcd(redc(sk),x);
      if(g>1){
        if(g<x)return g;
        for(int i=0;i<m;i++){
          ca=redc(__uint128_t(ca)*ca+e);
          cb=redc(__uint128_t(cb)*cb+e);
          cb=redc(__uint128_t(cb)*cb+e);
          unsigned long long c=redc(ca),d=redc(cb);
          unsigned long long cg=binary_gcd(c>d?c-d:d-c,x);
          if(cg>1){
            if(cg<x)return cg;
            else{
              e+=one;
              a=b=0;
              break;
            }
          }
        }
      }
    }
  };
  static unsigned long long st[64];
  int p=0;
  while(!(n&1)){
    n>>=1;
    ret.push_back(2);
  }
  if(n==1)return ret;
  st[p++]=n;
  while(p){
    unsigned long long now=st[--p];
    if(isprime(now)){
      ret.push_back(now);
      continue;
    }
    unsigned long long d=div(now);
    st[p++]=d;
    now/=d;
    if(now!=1)st[p++]=now;
  }
  return ret;
}
template<typename T>
std::enable_if_t<std::is_integral_v<T>,T>carmichael(T n){
  auto f=factorize(n);
  std::sort(f.begin(),f.end());
  T res=1;
  for(int l=0,r=0;l<f.size();l=r){
    while(r<f.size()&&f[l]==f[r])r++;
    if(f[l]==2){
      if(r-l==2)res=2;
      else if(r-l>=3)res=T(1)<<(r-l-2);
    }
    else{
      T prod=f[l]-1;
      for(int i=0;i<r-l-1;i++)prod*=f[l];
      res=std::lcm(res,prod);
    }
  }
  return res;
}
constexpr int carmichael_constexpr(int n){
  if(n==998244353)return 998244352;
  if(n==1000000007)return 1000000006;
  if(n<=1)return n;
  int res=1;
  int t=0;
  while(n%2==0){
    n/=2;
    t++;
  }
  if(t==2)res=2;
  else if(t>=3)res=1<<(t-2);
  for(int i=3;i*i<=n;i++)if(n%i==0){
    int c=0;
    while(n%i==0){
      n/=i;
      c++;
    }
    int prod=i-1;
    for(int j=0;j<c-1;j++)prod*=i;
    res=std::lcm(res,prod);
  }
  if(n!=1)res=std::lcm(res,n-1);
  return res;
}
template<int m>
struct mod_int{
private:
  static constexpr unsigned int umod=static_cast<unsigned int>(m);
  static constexpr unsigned int car=carmichael_constexpr(m);
  using uint=unsigned int;
  using mint=mod_int;
  uint v;
  static_assert(m<uint(1)<<31);
  mint sqrt_impl()const{
    if(this->val()<=1)return *this;
    if constexpr(m%8==1){
      mint b=2;
      while(b.pow((m-1)/2).val()==1)b++;
      int m2=m-1,e=0;
      while(m2%2==0)m2>>=1,e++;
      mint x=this->pow((m2-1)/2);
      mint y=(*this)*x*x;
      x*=*this;
      mint z=b.pow(m2);
      while(y.val()!=1){
        int j=0;
        mint t=y;
        while(t.val()!=1)t*=t,j++;
        z=z.pow(1<<(e-j-1));
        x*=z;
        z*=z;
        y*=z;e=j;
      }
      return x;
    }
    else if constexpr(m%8==5){
      mint ret=this->pow((m+3)/8);
      if((ret*ret).val()==this->val())return ret;
      else return ret*mint::raw(2).pow((m-1)/4);
    }
    else{
      return this->pow((m+1)/4);
    }
  }
public:
  using value_type=uint;
  mod_int():v(0){}
  template<typename T,std::enable_if_t<std::is_signed_v<T>,std::nullptr_t> =nullptr>
  mod_int(T a){
    a%=m;
    if(a<0)v=a+umod;
    else v=a;
  }
  template<typename T,std::enable_if_t<std::is_unsigned_v<T>,std::nullptr_t> =nullptr>
  mod_int(T a):v(a%umod){}
  static constexpr mint raw(int a){
    mint ret;
    ret.v=a;
    return ret;
  }
  inline uint val()const{return this->v;}
  static constexpr int mod(){return m;}
  inline mint &operator+=(const mint &b){
    this->v+=b.v;
    if(this->v>=umod)this->v-=umod;
    return *this;
  }
  inline mint &operator-=(const mint &b){
    this->v-=b.v;
    if(this->v>=umod)this->v+=umod;
    return *this;
  }
  inline mint &operator*=(const mint &b){
    this->v=((unsigned long long)this->v*b.v)%umod;
    return *this;
  }
  inline mint &operator/=(const mint &b){
    *this*=b.inv();
    return *this;
  }
  inline mint operator+()const{return *this;}
  inline mint operator-()const{return mint()-*this;}
  friend inline mint operator+(const mint &a,const mint &b){return mint(a)+=b;}
  friend inline mint operator-(const mint &a,const mint &b){return mint(a)-=b;}
  friend inline mint operator*(const mint &a,const mint &b){return mint(a)*=b;}
  friend inline mint operator/(const mint &a,const mint &b){return mint(a)/=b;}
  friend inline bool operator==(const mint &a,const mint &b){return a.val()==b.val();}
  friend inline bool operator!=(const mint &a,const mint &b){return !(a==b);}
  inline mint operator++(int){
    mint ret=*this;
    *this+=1;
    return ret;
  }
  inline mint operator--(int){
    mint ret=*this;
    *this-=1;
    return ret;
  }
  mint pow(long long n)const{
    mint ret=mint::raw(1),a(*this);
    while(n){
      if(n&1)ret*=a;
      a*=a;
      n>>=1;
    }
    return ret;
  }
  inline mint inv()const{
    assert(this->v!=0);
    return pow(car-1);
  }
  std::optional<mint>sqrt()const{
    if(this->val()<=1||this->pow((m-1)/2)==1)return std::make_optional(this->sqrt_impl());
    else return std::nullopt;
  }
  static constexpr unsigned int order(){return car;}
  friend std::istream &operator>>(std::istream &is,mint &b){
    long long a;
    is>>a;
    b=mint(a);
    return is;
  }
  friend std::ostream &operator<<(std::ostream &os,const mint &b){
    os<<b.val();
    return os;
  }
};
template<int m>
struct std::hash<mod_int<m>>{
  std::size_t operator()(mod_int<m>x)const{
    return std::hash<unsigned int>()(x.val());
  }
};
using mint998=mod_int<998244353>;
using mint107=mod_int<1000000007>;
using mint=mint998;
void SOLVE(){
  int n,m;
  string s;
  cin>>n>>m>>s;
  mint ans=0;
  vector<vector<int>>g(n);
  rep(i,m){
    int u,v;
    cin>>u>>v;
    u--,v--;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  string aoi="aoi?";
  int q=count(all(s),'?');
  rep(i,n){
    if(s[i]!='?'&&s[i]!='o')continue;
    int cnt[4]={0,0,0,0};
    for(int j:g[i]){
      rep(k,4)if(s[j]==aoi[k])cnt[k]++;
    }
    int fr=q-(s[i]=='?');
    ans+=mint(cnt[0])*cnt[2]*mint(26).pow(fr);
    if(cnt[3]){
      ans+=mint(cnt[0])*cnt[3]*mint(26).pow(fr-1);
      ans+=mint(cnt[2])*cnt[3]*mint(26).pow(fr-1);
      if(cnt[3]>=2){
        ans+=mint(cnt[3])*(cnt[3]-1)*mint(26).pow(fr-2);
      }
    }
  }
  cout<<ans<<endl;
}