#include <stdio.h>
#define L  27
inline int zero(int n)  {
    int total = 0;
    while(n)  {
        total += n / 5;
        n /= 5;
    }
    return total;
}

inline int caut2(int x)  {
    int r = 0;
    int pos = 1 << L;
    while(pos)  {
        if(r + pos <= 1 << L && zero(r + pos) < x)
            r += pos;
        pos /= 2;
    }
    if(x == zero(r + 1))
    return r + 1;
    return -1;
}
FILE *fin, *fout;
int main()  {
    fin = fopen("fact.in", "r");
    fout = fopen("fact.out", "w");
    int p;
    fscanf(fin, "%d", &p);
    fprintf(fout, "%d", caut2(p));
    fclose(fin);
    fclose(fout);
    return 0;
}