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

int numc(int x){
    int i=1;
    if(x==0){
        return 0;
    }
    while(x>=10){
        x /= 10;
        i++;
    }
    return i;
}

int vprimo(int b){
    int n;
    for(n=2; n<=b; n++){
            int t = b%n;
            if(t==0){
                if(b!=n){
                    return -1;
                }
                else{
                    return b;
                }
            }
        }
}

int main()
{
    int i = -1;
    int v[100];
    do{
        i++;
        scanf("%d", &v[i]);
    }
    while(v[i]!=-1);
    for(i=0; i<=sizeof(v); i++){
        if(v[i]==-1){
            break;
        }
        else{
            int n = v[i];
            int p = -1;
            while(numc(v[i])>=1){
                if(v[i]==1){
                    p = 1;
                    break;
                }
                p = vprimo(v[i]);
                if(p!=-1){
                    v[i]/=10;
                    continue;
                }
                else{
                    break;
                }
            }
            if(p==-1){
                printf("%d NON VALIDO\n", n);
            }
            else{
                printf("%d VALIDO\n", n);
            }
        }
    }
    return 0;
}