#include <stdio.h>
using namespace std;
int legendre(int n) {
    int cate = 0;
    while ( n > 0 ) {
        cate += n / 5;
        n /= 5;
    }
    return cate;
}
int cb(int n) {
    int pos, step, e = n;
    for ( pos=-1, step = (1 << 30); step; step >>= 1)
        if (legendre(pos + step) <= e)
            pos += step;
    if (legendre(pos) != e)
        return -1;
    return pos;
}
int main() {
    FILE *fin, *fout;
    int n;
    
    fin = fopen("fact.in", "r");
    fscanf( fin, "%d", &n );
    fclose( fin );
    
    fout = fopen("fact.out", "w");
    fprintf(fout, "%d\n", (n == 0? 1: cb(n)) );
    fclose( fout );
    
    return 0;
}