HDU 6182 A Math Problem 水题

#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <cstring>
#include <iterator>
#include <cmath>
#include <algorithm>
#include <stack>
#include <deque>
#include <map>
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define mem0(a) memset(a,0,sizeof(a))
#define sca(x) scanf("%d",&x)
#define de printf("=======\n")
typedef long long ll;
using namespace std;

ll n;
ll a[20];

ll qpower( ll a, ll b ) {
    ll res = 1;
    while( b ) {
        if( b & 1 ) res = res * a;
        b >>= 1;
        a = a * a;
    }
    return res;
}

void init() {
    for( int i = 1; i <= 15; i++ ) {
        a[i] = qpower(i, i);
    }
//    for( int i = 1; i <= 15; i++ ) {
//        cout << a[i] << " ";
//    }
//    cout << endl;
}
int main() {
    init();
    while( cin >> n ) {
        int i=0;
        for( i = 1; i <= 15; i++ ) {
//            cout << n << " " << a[i] << endl;
            if( n < a[i] ) break;
        }
        if( i == 16 && n == 437893890380859375 ) {
            cout << 15 << endl;
        }
        else if( i == 16 ) {
            cout << 15 << endl;
        }
        else {
            cout << i-1 << endl;
        }
    }
}