include

include

using namespace std; int main() {

int n,c;
long long int b=0;
string x;
cin>>n;
cin>>x;
c=x.size();
for(int k=c-1,l=1; k>=0; k--) {
	int m=x[k]-'0';
	b=m*l+b;
	l=l*n;
}
cout<<b;
return 0;

}