#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long LL;
const LL mod=1e9+7,N=1e6+10;
char s[N];
int main(){
	LL a;
	cin>>a>>(s+1);
	int n=strlen(s+1);
	long long ans=0,t=0,pre1=1,pre2=1;
	for(int i=n;i>=1;i--){
		if(i!=1){
			pre1=1ll*pre1*a%mod;
			ans=ans+1ll*(pre1-pre2+mod)*(n-i)%mod;
			ans%=mod;
			pre2=1ll*pre2*a%mod;
		}
	}
	for(int i=1;i<=n;i++){
		t=(1ll*t*a+(s[i]-'0'))%mod;
	}
	ans+=1ll*(t-pre2+1+mod)*(n-1);
	ans%=mod;
	cout<<ans;
	return 0;
}