#include <iostream>
#include <cstdio>
#define nmax 400000016
using namespace std;

int n,p,sol,crt,nr;

inline int nr5(int a)
{
    int nr=0;
    while(a>0)
    {
         nr+=a/5;
         a/=5;
    }
    return nr;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    int mid,st=1,dr=nmax;
    while(st<dr)
    {
        mid=(st+dr)/2;
        crt=nr5(mid);
        if(crt==p) { while(mid%5) mid--; printf("%d\n",mid); return 0;}
        if(crt<p) st=mid+1;
        if(crt>p) dr=mid-1;
    }
    printf("-1");
    fclose(stdin);
    fclose(stdout);
    return 0;
}