#include<bits/stdc++.h>
#define ll long long
const ll mod =1e9+7;
using namespace std;
string s;

ll POW(ll a,ll b){
    ll sum=1;
    while(b){
        if(b&1) sum=(sum%mod*a%mod)%mod;
        a=(a%mod*a%mod)%mod;
        b>>=1;
    }
    return sum;
}
int main(){
    ios::sync_with_stdio(false);
    ll a;cin>>a;
    cin>>s;

    ll ans=0;

    ll sum=0;
    for(int i=0;i<s.size()-1;i++){
        ans+=i*POW(a,i+1)-i*POW(a,i);
        ans=(ans%mod+mod)%mod;
    }

    for(int i=0;i<s.size();i++){
        sum=sum*a%mod;
        sum+=(s[i]-'0');
        sum%=mod;
    }

    sum=sum-POW(a,s.size()-1)+1;
    sum=(sum%mod+mod)%mod;
    ans+=sum*(s.size()-1);
    ans=(ans%mod+mod)%mod;
    cout<<ans<<endl;
    return 0;
}