#include <stdio.h>

int how_many_5(int n){

	int nr = 0;

	while(n > 1){

		if(n % 5 == 0){

			nr ++;
			n = n / 5;
		}
		else {

			n = 0;
		}
	}
	return nr;
}

int main(){

	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);

	int p, nr = -5, s = 0, ok = 0; 
	scanf("%d\n", &p);

	if(p == 0){
		
		ok = 2;
	}

	while(ok == 0){

		nr += 5;
		s += how_many_5(nr);

		if(s == p){

			ok = 1;
		}

		if(s > p){

			ok = 3;
		}
	}
	
	switch(ok){

		case 1:
			printf("%d\n", nr);
			break;

		case 2:
			printf("1\n");
			break;

		case 3:
			printf("-1\n");
			break;
	}

	return 0;
}