#include<stdio.h>

int min(int a, int b){

	if( a < b )
		return a;
	else
		return b;
}

int max(int a, int b){

	if( a > b )
		return a;
	else
		return b;
}

int nz(int a){

	int  p = 5, s = 0;
        
	while( p <= a ){
		s += a/p;
		p *= 5;	
	}	

	return s;
}

int main(){
	
	FILE* f = fopen("fact.in", "r");
	FILE* g = fopen("fact.out", "w");
	
	int p = 0, nr_cif = 0, val = 1;

	fscanf(f, "%d", &p);

	while( 1 ){
		
		nr_cif = nz(val);
		if( nr_cif == p){
			
			fprintf(g, "%d", val);
			break;
		}
		val++;
	}
	fclose(f);
	fclose(g);


	return 0;
}