#include <fstream>
#include <iostream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int factorial(int n)
{int p=1,a=0,b=0,c;
for(int i=2;i<=n;i++)
{c=i;while(c%2==0){a++;c/=2;}while(c%5==0){b++;c/=5;}}
if(a>b)return b;
return a;
}
int main()
{
    int P;
    f>>P;
    for(int i=1;;i++)if(factorial(i)==P){g<<i;break;}

    return 0;
}