#include <stdio.h>
#include <stdlib.h>
int  power(int x){
	int p=1;
	for(int i=1;i<=x;i++) p=p*5;
	return p;
}
int main(void) {
   int a = 0, b = 0, i = 1, nr0;
   FILE *f,*g;
   f = fopen("factorial.in", "r");
   g = fopen("factorial.out", "w");
   fscanf(f, "%d", &nr0);
   while(b<nr0) {
	a = a + 5;
	b = 0;
	i= 1;
   	while(a>=power(i)) {
		b = b + a/power(i);
		i++;
		}
	
   }
   fprintf(g,"%d\n", a);
   return 0;

}