#include<stdio.h>
#include<iostream.h>
int main(void){
 long p,i,n;
 FILE *in=fopen("fact.in","rt"),*out=fopen("fact.out","w+");
 fscanf(in,"%ld",&p);
 for(i=0;i<=100000;i++)
  if((i/5+i/25)==p){
   n=i;
   break;
   }

 if(i==100000) fprintf(out,"%ld",i);
 fprintf(out,"%ld",i);
}