#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(){
int i,j,k,l,temp,pcount = 40,length;
char string1[20],string2[20];
long test,answer = -1;
long check[] = {  2,  3,  5,  7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
	       , 53, 59, 61, 67, 71, 73, 79, 83, 89, 97,101,103,107,109,113
	       ,127,131,137,139,149,151,157,163,167,173};
long prime[3401];

for(i = 0;i < 40;i++)
	prime[i] = check[i];
for(i = 174;i <= 31623;i++){
	temp = 0;
	for(j = 0;j < 40;j++)
		if(i % check[j] == 0){
			temp = 1;
			break;
			}
	if(temp == 0)
		prime[pcount++] = i;
	}

scanf("%s",string1);
length = strlen(string1);
for(i = 0;i < length;i++)
	for(j = i;j < length;j++){
		for(k = i;k <= j;k++)
			string2[k - i] = string1[k];
		string2[k - i] = '\0';
		test = atol(string2);
		temp = 0;
		for(l = 0;l < pcount && prime[l] * prime[l] <= test;l++)
			if(test % prime[l] == 0){
				temp = 1;
				break;
				}
		if(temp == 0 && test != 1 && test != 0 && test > answer)
			answer = test;
		}
if(answer == -1)
	printf("No Primes\n");
else
	printf("%ld\n",answer);
return 0;
}