#include<fstream>

using namespace std;

ifstream cin("fact.in");
ofstream cout("fact.out");

int n;

int zero(int n){
    int nrz=0;
    while(n>=5){
            nrz+=n/5;
            n/=5;
    }
    return nrz;
}

int cautbin(int p){
    int r=0, pas=1<<30;
    while(pas!=0){
            if(zero(r+pas)<p){
                    r+=pas;
            }
            pas/=2;
    }
    return r+1;
}

int main(){
    cin>>n;
    cout<<cautbin(n);
    return 0;
}