#include <iostream>
#include <fstream>
using namespace std;

int main()
{ifstream f("fact.in");
ofstream g("fact.out");
unsigned long long int p;
unsigned long int counter=0;
unsigned long long int x=1;
f>>p;
while(counter!=p){
        int y=x;
    while(y%5==0){
        counter++;
        y/=5;
    }
    x++;

}
if(p==0){
    g<<1;
}else
g<<x-1;

    return 0;
}