#include <iostream>

#define Nmax 0x3f3f3f3f

using namespace std;

int numOfZeros(int n) {
    int z = 0;

    while (n != 0) {
        z += n / 5;
        n /= 5;
    }

    return z;
}

int cautBin(int left, int right, int p) {
    int mid = (right - left) / 2 + left, z = numOfZeros(mid);

    if (left == right || left + 1 == right) {
        return ((z == p) ? left : (numOfZeros(right) == p) ? right : -1);
    }

    if (z >= p) {
        return cautBin(left, mid, p);
    } else {
        return cautBin(mid + 1, right, p);
    }
}

int main()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);

    int p;

    scanf("%d", &p);

    printf("%d", cautBin(1, Nmax, p));

    return 0;
}