#include <cstdio>
using namespace std;

int lg;

int zero(int x)
{
    int z;
    if(x<5)
        z=x;
    else z=0;
    while(x>5)
    {
        x/=5;
        z+=x;
    }
    return z;
}

int cautbin(int lg,int p)
{
    int i=0;
    for(i=0;lg!=0;lg>>=1)
    {
        if(i+lg<=1000000000 && zero(i+lg)<=p)
            i+=lg;
    }
    return i;
}

int main()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    int p;
    scanf("%d", &p);
    printf("%d", cautbin(134217728,p));


    return 0;
}