#include<algorithm>   
using namespace std;   
int p;   
void solve(){   
    int i,k,x;   
    scanf("%d",&p);   
    if(p==0)   
        printf("1");   
    else   
        for(i=5; k<p; i+=5){   
            k=0;   
            for(x=i; x; k+=x/=5);   
            if(k==p)
                break;}
    if(k==p)
        printf("%d",i);
    else
        printf("-1");}   
int main(){   
    freopen("fact.in","r",stdin);   
    freopen("fact.out","w",stdout);   
    solve();   
    return 0;}