#include <stdio.h>

FILE *fi = fopen("fact.in", "r");
FILE *fo = fopen("fact.out", "w");

unsigned long P, i=0, k=0, V1=0, V2=0;
unsigned int n5(unsigned long N) {
	unsigned int k = 0;
	while (N%5==0) { k++; N/=5; }
	return k;
}

int main() {
	fscanf(fi, "%ld", &P);

	if (P==0) fprintf(fo, "1\n");
	else {
		do { 
			i+=5; 
    	    V2 = V1+n5(i);
			V1 = V2;
		   }
		while (V2<P);
		if (V2==P) fprintf(fo, "%ld\n", i);
		      else fprintf(fo, "-1\n");
	}

	fclose(fi);
	fclose(fo);

	return 0;
}