#include <stdio.h>
#define fr(i,a,b) for(int i=a;i<b;++i)
int sum(int i){
    int s=i;
    while(i) s+=i=i/5;
    return s;
    }

int main(){
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int n,m;
    scanf("%i",&n);
    if(!n) {printf("1");return 0;}
    int left=1,right=n,center,scenter;
    while(1){
        if(left>right)break;
        center=(left+right)/2;
        scenter=sum(center);
        if(scenter==n) {printf("%i",5*center);return 0;}
        else if(scenter<n) left=center+1;
        else right=center-1;
        }
    printf("-1");
    return 0;
    }