C++ :

#include <cstdio>
#include <algorithm>
int isP(long long x){
    if(x < 2) return 0;
    if(x % 2 == 0) return x == 2;
    for(long long i=3; i*i<=x; i+=2) if(x % i == 0) return 0;
    return 1;
}
int main(){
    int n; if(scanf("%d", &n) != 1) return 0;
    int d[8];
    for(int i=0;i<n;i++) scanf("%d", &d[i]);
    long long best = -1;
    /* 枚举非空子集；对每个子集枚举全排列 */
    for(int mask = 1; mask < (1 << n); mask++){
        int sub[8], L = 0;
        for(int i=0;i<n;i++) if(mask & (1 << i)) sub[L++] = d[i];
        std::sort(sub, sub + L);
        do {
            if(sub[0] == 0) continue;
            long long v = 0;
            for(int i=0;i<L;i++) v = v * 10 + sub[i];
            if(isP(v) && v > best) best = v;
        } while(std::next_permutation(sub, sub + L));
    }
    printf("%lld\n", best);
    return 0;
}