#include <stdio.h>

int main(){
	FILE *fin,*fout;
	long int P,aux;
	int N,i,j;
	
	fin=fopen("fact.in","rt");
	fout=fopen("fact.out","wt");
	
	fscanf(fin,"%ld",&P);
	
	if (P==0){
		N=1;
		fprintf(fout,"%d",N);
		return 0;
	}
	
	aux=0;
	N=1;
	while (1){
		N++;
		aux=0;
		for (i=1;i<=N;i++){
			j=i;
			
			while(j%5==0){
				j/=5;
				aux++;
			}
		}
		
		if (aux==P){
			fprintf(fout,"%d",N);
			fclose(fin);
			fclose(fout);
			return 0;
		}
	}
	
	return 0;
}