#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long p,c,k;
long long cb(long long s, long long d) { /// cel mai mic nr nat n pt care n! are exact p cifre de 0
    long long mij, pos=d+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;
    if (p==0) g<<1;
    else
        g<<cb(0,99999999999999999);
    return 0;
}