#include <fstream>

using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long long n, i, nr;
int main()
{   f >> n;
    i = 1;
    nr = 0;
    if(n == 0){
        g << 1;
        return 0;
    }
    while(nr < n){
        long long x = i;
        while(x % 5 == 0){
            nr++;
            x = x / 5;
        }
        nr++;
        i++;
    }
    g << 5 * (i-1);
    return 0;
}