#include <stdio.h>
#define DIM 100001

int n,P;
int s,c;
int p,mij;
long long u;

int main(){
	
	FILE*f1=fopen("fact.in","r");
	FILE*f2=fopen("fact.out","w");
	
	fscanf(f1,"%d",&P);
	
	p = P;
	u = 5*P;
	
	while(p <= u){
		mij = p + (u - p)/2;
		
		s = 0;
		c = 5;
		
		while(c <= mij){
			s += mij / c;
			c *= 5;
		}
				
		if(s >= P)
			u = mij - 1;
		else
			p = mij + 1;
		
	}
	
	if(P == 0)
		fprintf(f2,"1");
	else	
		fprintf(f2,"%d",p);
	
	fclose(f1);
	fclose(f2);
	
	return 0;
}