#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int P;

int count5(int x)
{
    int p5=5;
    int cnt=0;
    while(x>=p5)
    {
        cnt+=(x/p5);
        p5*=5;
    }
    return cnt;
}

int caut(int left,int right)
{
    if(right>=left)
    {
        int mid=left+(right-left)/2;
        int nr5=count5(mid);
        if(nr5==P)
        {
            mid-=(mid%5);
            return mid;
        }
        if(nr5>P)return caut(left,mid-1);
        else return caut(mid+1,right);
    }
    return -1;
}

int main()
{
    fin>>P;
    if(!P)fout<<1;
    else{
        fout<<caut(1,5*P);
    }
    return 0;
}