#include <stdio.h>
FILE *fi, *fo;
long p, n, k=0, i=0, c=1, i2;
int main  (void) {
fi=fopen ("fact.in", "rt");
fo=fopen ("fact.out", "wt");
fscanf (fi, "%ld", &p);
if (p<0) fprintf (fo, "-1\n"); 
if (p==0) n=1; else {
while (k!=p) {
i+=5;
i2=i;
while (i2%5==0) {
k++; i2/=5;
} 
}
}
n=i;
fprintf(fo, "%ld", n);
fcloseall();
return 0;
}