#include<iostream>
using namespace std;
int suma(int n)
{
int s,prim,c,d;
while(n!=0)
{
c=n%10;
n=n/10;
prim=1;
for(d=2;(d<=c/2)&&(prim==1);d++)
{if(c%d==0)
prim==0;}
if(prim==1)
s=s+c;}
return s;
}
int main()
{
int n;
cin>>n;
cout<<suma(n)
;}
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