#include<fstream>
using namespace std;
ifstream in ("fact.in");
ofstream out ("fact.out");
int main (){
    int n=0,n1,i=0,p;
    in>>p;
    while(i<p){
        n+=5;
        n1=n;
        while(n1%5==0){
            i++;
            n1=n1/5;

    }
    }
    if(n==0)
    n++;
out<<n;
return 0;
}