#include <stdio.h>
#include <stdlib.h>

int  power(int x){
    int p=1;
    int i=1;
    for(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("fact.in", "r");
   g = fopen("fact.out", "w");
   fscanf(f, "%d", &nr0);
   if (nr0==0) {
     fprintf(g, "1\n");
     return 0;
   }
   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;
}