#include <cstdio>
using namespace std;


int n, P, p, u, m, nr, ok;

int zero (int m)
{
    int fact=5, nr=0;
    while (fact<=m){
        nr+=m/fact;
        fact*=5;
    }
    return nr;
}
int main (){
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);

    scanf("%d", &P);
    if (P==0) printf("1");
    else{
        p=1;
        u=5*P;
        while (p<=u){
            m=p+(u-p)/2;
            nr=zero(m);
            if (nr>=P) u=m-1;
            else p=m+1;
            if (nr==P) ok=1;
        }
        if (ok) printf("%d", p);
        else printf("-1");
    }
    return 0;
}