RT，死活过不了 test 3，本来今晚就打的不好，结果全盘皆输了。

//Author:Leftist_G / Shunpower
//Spade Su & Xiao Bao
//Hey Left
//Just enjoy the loneliness
//Open a personal party always stay
#include <bits/stdc++.h>
#define ET return 0
#define fi first
#define se second
#define mp make_pair
#define pb emplace_back
#define ll long long
#define ull unsigned long long
#define inf INT_MAX
#define uinf INT_MIN
#define pii pair<int,int>
#define pll pair<ll,ll>
#define debug puts("--------Chery AK IOI--------");
#define Yes cout<<"Yes"<<endl;
#define No cout<<"No"<<endl;
#define pt puts("")
#define fr1(i,a,b) for(int i=a;i<=b;i++)
#define fr2(i,a,b) for(int i=a;i>=b;i--)
#define fv(i,p) for(int i=0;i<p.size();i++)
#define ld long double
#define il inline
#define ptc putchar
using namespace std;
const int N=3e5+10;
namespace Shun{
    int lowbit(int x){
        return x&-x;
    }
    template <typename T>
    inline void read(T &x){
       T s=0,w=1;
       char ch=getchar();
       while(ch<'0'||ch>'9'){
            if(ch=='-'){
                w=-1;
            }
            ch=getchar();
        }
       while(ch>='0'&&ch<='9'){
            s=s*10+ch-'0';
            ch=getchar();
       }
       x=s*w;
    }
    template <typename T>
    inline void write(T x){
        if(x<0){
            putchar('-');
            x=-x;
        }
        if(x>9){
            write(x/10);
        }
        putchar(x%10+'0');
    }
}
using namespace Shun;
int n,q;
string s;
int l,r;
set <int> geq,leq;
ll fac[N],inv[N];
const ll M=998244353;
ll qpow(ll b,ll p,ll k){
    if(!p){
        return 1;
    }
    ll d=qpow(b,p>>1,k);
    if(p&1){
        return d*d%k*b%k;
    }
    else{
        return d*d%k;
    }
}
void init(int n=300000){
    fac[0]=1;
    fr1(i,1,n){
        fac[i]=1ll*fac[i-1]*i%M;
    }
    inv[n]=qpow(fac[n],M-2,M);
    fr2(i,n-1,0){
        inv[i]=1ll*inv[i+1]*(i+1)%M;
    }
}
ll C(int n,int m){
    return fac[n]*inv[m]%M*inv[n-m]%M;
}
struct BIT{
    int k[N];
    void insert(int p,int x){
        while(p<=n){
            k[p]+=x;
            p+=lowbit(p);
        }
    }
    int query(int p){
        int ans=0;
        while(p){
            ans+=k[p];
            p-=lowbit(p);
        }
        return ans;
    }
} T;
void work(){
    int per=r-l+1;
    if(geq.size()&&leq.size()){
        int x=*geq.begin(),y=*leq.begin();
        if(min(x,y)!=2){
            cout<<"0\n";
            return;
        }
        int len=T.query(max(*geq.begin(),*leq.begin()));
        assert(per>=len);
        // cout<0<"!"<<len<<endl;
        cout<<C(per,len)*fac[per-len]%M<<'\n';
    }
    else if(geq.size()){
        if(*geq.begin()!=2){
            cout<<"0\n";
        }
        else{
            cout<<fac[per-1]<<'\n';
        }
    }
    else if(leq.size()){
        if(*leq.begin()!=2){
            cout<<"0\n";
        }
        else{
            cout<<fac[per-1]<<'\n';
        }
    }
    else{
        cout<<"0\n";
    }
}
int main(){
#ifdef Griffin
    freopen(".in","r",stdin);
    freopen(".out","w",stdout);
#endif
    init();
    cin>>n>>q;
    cin>>s;
    s='@'+s;
    l=1,r=n;
    // cout<<inv[2]<<endl;
    T.insert(1,1);
    fr1(i,1,n-1){
        if(s[i]=='>'){
            r--;
            geq.insert(i+1);
        }
        else if(s[i]=='<'){
            l++;
            leq.insert(i+1);
        }
        else{
            T.insert(i+1,1);
        }
    }
    work();
    while(q--){
        int idx;
        char c;
        cin>>idx>>c;
        if(s[idx]=='<'){
            leq.erase(idx+1);
            if(c=='?'){
                T.insert(idx+1,1);
            }
            l--;
        }
        if(s[idx]=='>'){
            geq.erase(idx+1);
            if(c=='?'){
                T.insert(idx+1,1);
            }
            r++;
        }
        if(c=='<'){
            leq.insert(idx+1);
            if(s[idx]=='?'){
                T.insert(idx+1,-1);
            }
            l++;
        }
        if(c=='>'){
            geq.insert(idx+1);
            if(s[idx]=='?'){
                T.insert(idx+1,-1);
            }
            r--;
        }
        s[idx]=c;
        // cout<<s<<" "<<l<<" "<<r<<endl;
        work();
    }
    ET;
}
//ETERNAL LOVE FOR Zhang Junhao, Mu Zhicheng and Zuo Hang.
//ALL FOR Zhang Junhao.