#include<bits/stdc++.h>
using namespace std;
int a[10],n;
int ss(int w){
	if(w<2){
		return 0;
	}else{
		for(int i=2;i<=sqrt(w);i++){
			if(w%i==0){
				return 0;
			}
		}
		return 1;
	}
}
int as(int e){
	int s1=0,s2=0;
	for(int i=0;i<=e;i++){
		s1=s1*10+a[i];
	}
	for(int i=e+1;i<n;i++){
		s2=s2*10+a[i];
	}
//	cout<<s1<<" "<<s2<<" "<<s1+s2<<endl;
	return s1+s2;
}
int main(){
	int min=999;
	string s;
	cin>>s;
	n=s.size();
	for(int i=0;i<n;i++){
		a[i]=int(s[i]-48);
	}
	for(int i=0;i<n-1;i++){
		if(ss(as(i))&&as(i)<min){
			min=as(i);
		}
	}
	cout<<min;
	return 0;
}
/**************************************************************
	Problem: 1128
	User: zzz
	Language: C++
	Result: Wrong Answer
****************************************************************/