#include <iostream>
using namespace std;
int main()
{int n,p,i,aux,x2,x5;
cin>>p;n=1;
while(p!=0) {x5=0;x2=0;
                    for(i=1;i<=n;i++) {aux=i;
                                               if(aux%2==0) while(aux%2==0) {aux/=2;x2++;}
                                               if(aux%5==0) while(aux%5==0) {aux/=5;x5++;}
}
                    n++;
                    if(x2<x5) {if(x2==p) {p=0;n--;}}
                    else {if(x5==p) {p=0;n--;}}
}
      cout<<n;       
return 0;	
}