#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long p;

 long long fbin(){
     long long lo = 1, hi = 5 * p + 100, mid, cmid, exp, fin;
    while(lo < hi){
        mid = lo + (hi - lo) / 2;
        cmid = mid;
        exp =0;
        while(cmid >= 5){
            exp += cmid / 5;
            cmid /= 5;
        }
        if(exp < p){
            lo = mid + 1;
        }else{
            fin = mid;
            hi = mid ;
        }
    }
     return hi;
}

int main(){
    fin>>p;
    if(p == 0){
        fout<<1;
    }else{
        fout<<fbin();
    }
}