#include<iostream>
#include<fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
long long cate(long long n,long long k){
    long long a=0,x=1;
    while(n>=k){
        a+=n/k;
        n/=k;
    }
    return a;
}
long long cautbinar(long long P){
    long long r=0,pas= 1LL << 50;   // 1<<x inseamna 1 pe pozitia x in reprezentarea binara
    while(pas){
        if( cate( r+pas , 5 ) < P ) r+=pas;
        pas=pas>>1;
    }
    return r;
}
int main(){
    long long p;
    in>>p;
    out<< cautbinar(p) + 1 <<'\n';
    return 0;
}