#include <fstream>
using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

long long nrz(long long x){
    long long s=0;
    while(x>0){
        s=s+x/5;
        x=x/5;
    }
    return s;
}

int main()
{
    long long i=0,pas=1<<20,n;
    f>>n;
    while(pas!=0){
        if(nrz(i+pas)<=n-1)
            i+=pas;
        pas/=2;
    }
    g<<i+1;
    return 0;
}