#include<stdio.h>
int p;

int zero(int n)
{
    int r=0;
    while(n>=5)
        {r+=n/5;
        n/=5;
        }
    return r;
}


int main()
{long long pas,i,j;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
scanf("%d",&p);
pas=1<<30;
i=0;
while(pas!=0)
    {if(zero(i+pas)<p)
        i+=pas;
    pas/=2;
    }
j=i+1;
if(zero(j)==p)
    printf("%d",j);
else
printf("-1");
return 0;
}