/
11466.cpp
77 lines (59 loc) · 1.33 KB
/
11466.cpp
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#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;
int MAX_N = 10000000;
int main(void)
{
int *lp = new int[MAX_N];
vector<int> primes;
long long input;
fill(lp, lp + MAX_N, 0);
for (int i = 2; i < MAX_N; i++) {
if (lp[i] == 0) {
lp[i] = i;
primes.push_back(i);
}
for (int j = 0; j < primes.size() && primes[j] <= lp[i] && i * primes[j] < MAX_N; j++) {
lp[i * primes[j]] = primes[j];
}
}
while (cin >> input) {
if (input == 0) {
break;
}
bool negative = false;
bool found = false;
long long result = 0;
int divisor_count = 0;
if (input < 0) {
input = -input;
}
for (int i = 0, sz = primes.size(); i < sz; i++) {
if (primes[i] > input) {
break;
} else if (input == primes[i]) {
break;
} else if (input % primes[i] == 0) {
found = true;
result = primes[i];
divisor_count++;
do {
input /= primes[i];
} while (input % primes[i] == 0);
}
}
if (!found) {
cout << -1 << endl;
} else if (divisor_count < 2 && input == 1) {
cout << -1 << endl;
} else if (input > result) {
cout << input << endl;
} else {
cout << result << endl;
}
}
delete [] lp;
return 0;
}