#include <stdio.h>  
   int main(void)   
   {  
       freopen("fact.in", "r", stdin);  
       long P;  
       scanf("%ld", &P);  
       fclose(stdin);  
       int c=0, i=1, j;  
       while(c<P) {j=i;  
                   while (j%5==0) {c++;j=j/5;}  
                    i++;
                  }  
       freopen("fact.out", "w", stdout);  
       if (c==P) printf("%d", i-1);   
       else printf("%d", -1);  
       fclose(stdout);  
       return 0;  
   }