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

int main()
{
    int p,q, n=1,fact,c=0;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    int z=p*10;
    for(int i=1; i<=1000;i++)
    {
            fact=1;
            c++;
            for(int j=1; j<=i;j++)
            {
                    fact*=j;
                    }
            if(fact%z==0)
            {
            q=0;
            break;
            }
            }
    if(q==0)
    printf("%d",c);
    else
    printf("-1");
    fclose(stdin);
    fclose(stdout);
    return 0;
    }