#include<stdio.h>
int pow5(long unsigned n);
int main()
{
	long unsigned p;
   long unsigned sol;
   freopen("fact.in","r",stdin);
   freopen("fact.out","w",stdout);
   scanf("%d",&p);
   sol=(p*5)-(pow5(p)*5);
   if (p) printf("%lu\n",sol);
   else printf("1\n");
}
int pow5(long unsigned n)
{
	long unsigned p1=5,p2=25,p3=125,p4=625,p5=3125,p6=15625,p7=78125,p8=390625;
   long unsigned p9=1953125,p10=9765625,p11=48828125,p12=244140625;
   if(n>p12) return 12;
   if(n>p11) return 11;
   if(n>p10) return 10;
   if(n>p9) return 9;
   if(n>p8) return 8;
   if(n>p7) return 7;
   if(n>p6) return 6;
   if(n>p5) return 5;
   if(n>p4) return 4;
   if(n>p3) return 3;
   if(n>p2) return 2;
   if(n>p1) return 1;
   return 0;
}