/**
* Problem: Find the sum of all eleven primes that are both truncatable from left to right and right to left.
* Algorithm: DFS
* Author: daiwb
* Date: 2008/08/31
*/
#include
#include
#include
#include
using namespace std;
#define REP(i,n) for(int i=0;i<(n);++i)
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
typedef long long LL;
int res;
int num[4] = {1, 3, 7, 9};
int string2int(string str) {
stringstream ss;
ss << str;
int res;
ss >> res;
return res;
}
bool isprime(int val) {
if (val == 2 || val == 3 || val == 5 || val == 7) return true;
if (val == 1) return false;
int mid = (int)sqrt(val + 0.5);
if ((val & 1) == 0) return false;
for (int i = 3; i <= mid; i += 2) {
if ((val % i) == 0) return false;
}
return true;
}
bool isok(string str) {
if (str.length() == 1) return false;
REP(len,str.length()) {
string s = str.substr(len);
if (!isprime(string2int(s))) return false;
s = str.substr(0, len + 1);
if (!isprime(string2int(s))) return false;
}
return true;
}
void dfs(string str) {
stringstream ss;
ss << str;
int val;
ss >> val;
if (!isprime(val)) return;
if (isok(str)) {
res += val;
}
REP(i,4) dfs(str + char(num[i] + '0'));
}
void run() {
res = 0;
dfs("2");
dfs("3");
dfs("5");
dfs("7");
cout << res << endl;
}
int main() {
run();
}