#include <fstream>

using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");
int numarat(int n){
    int zero = 0;
    while(n > 0){
        zero = zero + (n/5);
        n = n / 5;
    }

    return zero;
}
int main()
{
    int pas,p,r;
    cin >> p;
    r = 0;
    pas = 1 << 30;
    while(pas != 0){
        if(numarat(r+pas) < p){
            r +=pas;
        }
        pas /= 2;
    }
    if(numarat(r+1) == p){
        cout << r+1;
    }else{
        cout << "-1";
    }
    return 0;
}