#include <stdio.h>

long p;
long long n;
void citire(){
     FILE *in;
     in=fopen("fact.in","r");

     fscanf(in,"%ld",&p);   
     fclose(in); 
     }
     
void scriere(){
FILE *out;
     out=fopen("fact.out","w");
     fprintf(out,"%lld",n);
     fclose(out);
     }

long nrz(long long i){
 if(i%5==0) return 1+nrz(i/5);
 else return 0;
}

void procesare(){
long long i;
long a=0;
n=1;
if(p>0){
 for(i=5;i<=50000000;i+=5){
  a=a+nrz(i);
  if(a==p){ n=i;break; }
  if(a>p) { n=-1;break;}
}
 }
 }
     
int main(){
 citire();
 procesare();
 scriere();
 return 0;   
}