#include <stdio.h>      
     
long n;      
long nr;      
     
void cit()      
{      
        FILE *f=fopen("fact.in", "r");      
        fscanf(f, "%ld", &n);      
        fclose(f);      
}      
     
void tip()      
{      
        FILE *f=fopen("fact.out", "w");      
        fprintf(f, "%ld\n", nr);      
        fclose(f);      
}      
     
void fct()      
{      
        int i=0,t;      
        while (nr<n)      
        {      
                i+=5;      
                nr+=5;      
                if (nr<n)      
                {      
                t=i;      
                do     
                {      
     
                        if (t%5==0) t/=5;      
                        nr++;      
                } while (t%5==0);      
                }      
                else     
                {      
                        i-=nr-n;      
                } 
		if (nr>n)
		{
			nr=-1;
			return;
		}     
        }      
        nr=5*i;   
        if (n==0) nr=1;   
}      
     
int main()      
{      
        cit();      
        fct();      
        tip();      
        return 0;      
}