#include <stdio.h>   
  
long n;   
long nr;   
  
void cit()   
{   
        FILE *f=fopen("fact.in", "r");   
        fscanf(f, "%ld", &n);   
        fclose(f);   
}   
  
void tip()   
{   
        FILE *f=fopen("fact.out", "w");   
        fprintf(f, "%ld\n", nr);   
        fclose(f);   
}   
  
void fct()   
{   
	int i, t;   
        while (nr<n)   
        {   
                i+=5;   
                nr+=5;   
                if (nr<n)   
                {   
                t=i;   
                do  
                {   
  
                        if (t%5==0) t/=5;   
                        nr++;   
                } while (t%5==0);   
                }   
                else  
                {   
                        i-=nr-n;   
                }   
        }   
        nr=5*i;   
	//if (!n) nr=1;
}   
  
int main()   
{   
        cit();   
        fct();   
        tip();   
        return 0;   
}