#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
const long long M=1000000000;
ifstream f("fact.in");
ofstream g("fact.out");
int n5(long long p)
{
    int pow = 1, s = 0;
    while ( pow * 5 <= p)
    {
        pow *= 5;
        s += p/pow;

    }
    return s;
}

long long dei(long long lo,long long hi,int p)
{
    long long m;
        while(hi-lo>1)
        {m=(lo+hi)/2;
        if(n5(m)<p)
        lo=m;
        else
        hi=m;
    }

        if(n5(hi)==p)
    return hi;
    else
        return -1;
        }


int main()
{

int p;
f>>p;
g<<dei(0,M,p);
    return 0;
}