#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
long long v[100000001];
int main()
{
    int p,i,m,st,dr,mijl,poz,k=0;
    in>>p;
    v[0]=0;
    if(p==0)out<<1;
    else{
        for(i=1;i<=p*5&&k==0;i++)
            {
                m=i;
                int cnt=0;
                while(m%5==0)
                {
                    cnt++;
                    m=m/5;

                }
                v[i]=v[i-1]+cnt;
                if(v[i]==p){
                    out<<i;
                    k=1;
                }
            }
    }

    return 0;
}