#include <cstdio>
int nr(int n)
{
    int p5 = 5,s=0;
    while(p5<=n)
        s+=n/p5,p5*=5;
    return s;
}
int main()
{
    int s;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&s);
    if(s==0)
        printf("1");
    else
    for(int i=0;true;i++)
    {
        if(nr(i)==s){
            printf("%d",i);break;
        }
    }
    return 0;
}