#include <cstdio>


using namespace std;


int P;


int zero (int x) {
int rez = 0;
while (x) {
rez += x / 5;
x /= 5;
}
return rez;
}


int BS (int p) {
int i, pas = 1 << 30;
for (i = 0; pas; pas >>= 1) {
if (zero(i + pas) < p) {
i += pas;
}
}
return i + 1;
}


int main () {
freopen ("fact.in", "r", stdin);
freopen ("fact.out", "w", stdout);
scanf ("%d", &P);
if (zero(BS(P)) == P) {
printf ("%d", BS(P));
}
else {
printf ("-1");
}
return 0;
}