#include <stdio.h>

using namespace std;

long long int Binary_Search(long long int n)
{
    long long int l = 1, r = 1e16, m;
    while(l < r) 
    {
        m = (l + r) / 2;
        if(Count(m) < n) {
            l = m + 1;
        }
        else {
            r = m;
        }
    }
    return l;
}
    
long long int Count(long long int n)
{
    long long int p = 0;
    while(n)
    {
        p += n / 5;
        n /= 5;
    }
    return p;
}

int main()
{
    freopen("fact.in",r,stdin);
    freopen("fact.out",w,stdout);
    long long int n, p;
    
    scanf("%d",&p);
    n = Binary_Search(p);
    printf("lld\n",n); 
    
    return 0;
}