#include <cstdio>
using namespace std;

int p;

int main()
{
    int i,n,ok;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    if(p==0)
    {
        printf("1");
        return 0;
    }
    fclose(stdin);
    for(i=p;;i++)
    {
        n=i;ok=0;
        while(n/5!=0)
        {
            n/=5;
            ok+=n;
        }
        if(ok==p)
        {
            printf("%d\n",i);
            return 0;
        }
        if(ok>p)
        break;
    }
    printf("-1\n");
    fclose(stdout);
    return 0;
}