#include<bits/stdc++.h>
#define ll long long
#define N 1000005
using namespace std;

ll pw(ll x, ll y){

    ll ret=1;
    for (;y;y>>=1,x=x*x)
        if (y&1){
            ret*=x;
            if (__int128(ret)>__int128(1e18)) return -1;
        }
    return ret;
}

bool mark[N];
int cnt,prim[N],d[N],num[N];

void initial(){
    cnt = 0;
    d[1]=1;
    for (int i=2;i<N;i++){
        if (!mark[i]){
            prim[cnt++]=i;
            num[i]=1;
            d[i]=2;
        }
        for (int j=0;j<cnt&&i*prim[j]<N;j++){
            mark[i*prim[j]]=1;
            if (!(i%prim[j])){
                num[i*prim[j]] = num[i]+1;
                d[i*prim[j]] = d[i]/(num[i]+1)*(num[i*prim[j]]+1);
                break;
            }
            d[i*prim[j]]=d[i]*d[prim[j]];
            num[i*prim[j]]=1;
        }
    }
}

bool pd(ll n){
    for (int i=0;i<cnt;i++)
        if (n%prim[i]==0) return false;
    return true;
}

int main() {
    ll s;
    scanf("%lld", &s);
    initial();
    for (int i=1;i<=1000000;i++)
        if (pw(i,d[i])==s){
            printf("%lld",i);
            return 0;
        }

    ll n2 = sqrt(s)-1.000;
    while(n2*n2<s)n2++;
    if (n2*n2==s&&pd(n2)){
        printf("%lld\n",n2);
        return 0;
    }
    printf("-1\n");
}