#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int aflare(int x)
{
    int put=5,cnt=0;
    while(x>=put)
    {
        cnt+=x/put;
        put=put*5;
    }
    return cnt;
}
int caut(int n)
{
    int st=1;
    int dr=(1 << 30);
    int ans=1;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(aflare(mij)<n)
            st=mij+1;
        else if(aflare(mij)>n)
            dr=mij-1;
        else
            ans=mij;
    }
    return ans;
}
int main()
{
    int p;
    in>>p;
    out<<caut(p);
    return 0;
}