#include <cstdio>

using namespace std;

int main(){
    long long int p,i,k,aux;
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%lld",&p);
    if(p == 0){
        printf("1\n");
    }else{
       k = 4 * p;
       i = 25;
       while(k/i != 0){
            k = k + k/i;
       }
       if(k > p){
            printf("-1\n");
       }else{
            printf("%lld\n",k);
       }
    }
    return 0;
}