#include <cstdio>
using namespace std;
int legendre(int n, int f){
    int ans = 0;
    long long cf = f;
    while (cf <= n){
        ans += n / cf;
        cf *= f;
    }
    return ans;
}
int bs(int st, int dr, int p){
    int med, last = 1;
    while (st <= dr){
        med = (st + dr) >> 1;
        if (legendre(med, 5) <= p){
            last = med;
            st = med + 1;
        }
        else{
            dr = med - 1;
        }
    }
    return last;
}
int main(){
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    int p;
    scanf("%d", &p);
    if (p == 0)
        printf("1\n");
    else
        printf("%d", bs(1, 40000010, p) / 5 * 5);
    return 0;
}