//FACTORIAL

#include<iostream.h>
#include<fstream.h>
long putere5(int k){
     if(k ==0) return 1;
     return 5*putere5(k-1);
}
int main(){
    long n,p,i,j,k;
    ifstream in("factorial.in");
    ofstream out("factorial.out");
    in>>p;
    //cin>>p;
    n = 0;i = 0;
    while(i<p){
                n+=5;
                i++;
                for(j = 2;j<=20;j++)
                      if(n%putere5(j)==0) i++;
                      else break;
                
    }
    out<<n<<endl;
    //getch();
    in.close();
    out.close();
    return 0;
}