#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int n, m, v[100], p;

int countzero(int n){
    int d=5;
    int rez=0;
    while(d<=n)
    {
        rez+=n/d;
        d*=5;
    }
    return rez;
}

int dim(int st, int dr){
    int mid = (st+dr)/2, ctz = countzero(mid);
    if(st == dr || ctz == p){
        while(countzero(mid) >= p) mid--;
        mid++;
        if(countzero(mid) == p) return mid;
        else return -1;
    }
    else if(ctz > p) return dim(st, mid);
    else return dim(mid+1, dr);
}

int main()
{
    int i, j;
    f >> p;
    if(p == 0){
        g << 1;
        return 0;
    }
    g << dim(1, 100000);

    return 0;
}