#include<stdio.h>

int fac(int n) {
if ( n == 0 )
	return 1;
else return n*fac(n-1);
}

int main(){
int n=0,p,i=0;
FILE *in,*out;

in = fopen("fact.in","r");
fscanf(in,"%d",&p);

int temp=0;
int temp1=0;
  while ( temp < p) {
    n++;
    temp1= n;
    while ( temp1%5==0) {
       temp++;
       temp1=temp1/5;
     }
 i=n;
}



fclose(in);
out = fopen("fact.out","w");
fprintf(out,"%d",i);
fclose(out);
return 0;
}