Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i,n) for (ll i=0;i<(n);++i)
const ll MOD=998244353;

template<uint_fast64_t Modulus> class modint{
    using u64=uint_fast64_t;
    public:
    u64 a;
    constexpr modint(const u64 x=0) noexcept:a(((x%Modulus)+Modulus)%Modulus){}
    constexpr u64 &value() noexcept{return a;}
    constexpr const u64 &value() const noexcept{return a;}
    constexpr modint &operator+=(const modint &rhs) noexcept{
        a+=rhs.a;
        if (a>=Modulus) a-=Modulus;
        return *this;
    }
    constexpr modint operator+(const modint &rhs) const noexcept{
        return modint(*this)+=rhs;
    }
    constexpr modint &operator++() noexcept{
        return ++a,*this;
    }
    constexpr modint operator++(int) noexcept{
        modint t=*this; return ++a,t;
    }
    constexpr modint &operator-=(const modint &rhs) noexcept{
        if (a<rhs.a) a+=Modulus;
        a-=rhs.a;
        return *this;
    }
    constexpr modint operator-(const modint &rhs) const noexcept{
        return modint(*this)-=rhs;
    }
    constexpr modint &operator--() noexcept{
        return --a,*this;
    }
    constexpr modint operator--(int) noexcept{
        modint t=*this; return --a,t;
    }
    constexpr modint &operator*=(const modint &rhs) noexcept{
        a=a*rhs.a%Modulus;
        return *this;
    }
    constexpr modint operator*(const modint &rhs) const noexcept{
        return modint(*this)*=rhs;
    }
    constexpr modint &operator/=(modint rhs) noexcept{
        u64 exp=Modulus-2;
        while(exp){
            if (exp&1) *this*=rhs;
            rhs*=rhs; exp>>=1;
        }
        return *this;
    }
    constexpr modint operator/(const modint &rhs) const noexcept{
        return modint(*this)/=rhs;
    }
    constexpr modint operator-() const noexcept{
        return modint(Modulus-a);
    }
    constexpr bool operator==(const modint &rhs) const noexcept{
        return a==rhs.a;
    }
    constexpr bool operator!=(const modint &rhs) const noexcept{
        return a!=rhs.a;
    }
    constexpr bool operator!() const noexcept{return !a;}
    friend constexpr modint pow(modint rhs,long long exp) noexcept{
        modint res{1};
        while(exp){
            if (exp&1) res*=rhs;
            rhs*=rhs; exp>>=1;
        }
        return res;
    }
    friend ostream &operator<<(ostream &s,const modint &rhs) noexcept {
        return s << rhs.a;
    }
    friend istream &operator>>(istream &s,modint &rhs) noexcept {
        u64 a; rhs=modint{(s >> a,a)}; return s;
    }
};

using mint=modint<MOD>;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N; string X; cin >> N >> X;
    vector<mint> cnt(N+1,0),exc(N+1,0);
    rep(i,N) cnt[i+1]=cnt[i]*2+(X[i]-'0');
    mint ans=0;
    for (int i=1;i<=N;++i){
        if (N%i!=0||!((N/i)&1)) continue;
        int n=N/i; mint c=cnt[i]+1;
        string a=X.substr(0,i),b,check;
        for (char x:a) b+=(x=='1'?'0':'1');
        rep(i,n) check+=(i%2&1?b:a);
        c-=(check>X);
        for (int x:divisor(i)) if ((i/x)&1) c-=exc[x];
        exc[i]=c; ans+=c*2*i;
    }
    cout << ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:102:20: error: 'divisor' was not declared in this scope
  102 |         for (int x:divisor(i)) if ((i/x)&1) c-=exc[x];
      |                    ^~~~~~~