#include <fstream>
#include <iostream>
#include <algorithm>
using namespace std;
ifstream f("fact.in"); ///kruskal
ofstream g("fact.out");
int p,c,k;
int cb(int s, int d) { /// cel mai mic nr nat n pt care n! are exact p cifre de 0
    int mij, pos=1, k5, c;
    while(s<=d) {
        mij = s +(d-s)/2;
        c=5, k5=0; while (c<=mij) k5+=mij/c, c*=5;
        if(p>k5) s=mij+1;
        else pos=mij, d = mij-1;
    }
    return pos;
}

int main()
{
    f>>p;
    g<<cb(1,2000000000);
    return 0;
}