#include <stdio.h>
#include <stdlib.h>
int fact(int n)
{
    int k=0;
    while(n%5==0)
    {
        n=n/5;
        k++;
        if(n%5==0)
        {
            n=n/5;
            k++;
        }
    }
    return k;
}
int main()
{
    FILE *f =fopen("fact.in","r");
    FILE *g =fopen("fact.out","w");
    int p;
    fscanf(f,"%d",&p);
    int i,k=0;
    if(p==0)
    {
        fprintf(g,"1");
        return 0;
    }

    for(i=1; i<=p; i++)
    {
        k=k+fact(i*5);
        if(k==p)
        {
            fprintf(g,"%d",i*5);
            break;
        }
        if(k>p)
        {
            fprintf(g,"-1");
            break;
        }
    }

    return 0;
}