#include<stdio.h>
#include<string.h>
#define DIM 10000
int main(){

int n = 0,d = 0,c = 0,p,i,j,k,z = 0;

FILE *f = fopen ("fact.in","r");
FILE *g = fopen ("fact.out","w");

fscanf(f,"%d",&p);
int ok = 0,b = 0;

k = 0;
int m ;
for(i=1;i<=DIM;i++){
	n++;
        
	for(j=1;j<=n;j++){
	    m = j;

	    
            for(b=1;b<=n;b++)
		if(m%10 == 0) {
			z++;
			m=m/10;
			}
              
            for(b=1;b<=n;b++)
		if(m%2 == 0) {
			d++;
			m=m/2;
			}
                
	   for(b=1;b<=n;b++)       
		if(m%5 == 0) {
			c++;
                        m=m/5;
			}
            
		if(d>c){
			k=c;
                   }
		else {
			k=d;
                    }
		if((k+z) == p) {
			ok= 1;
			break;
                        }
	}
	z = 0;
	k = 0;
	c = 0;

	if(ok == 1)
        	break;
	}
fprintf(g,"%d",n);
fclose(f);
fclose(g);
return 0;
}