Trees in a Wood UVA

太坑惹,,,没用longlong各种WA

#include <iostream>
#include <string.h>
#include <cstdio>
#include <math.h>
#define SIGMA_SIZE 26
#pragma warning ( disable : 4996 )

using namespace std;
typedef long long LL;

inline int Max(int a,int b) { return a>b?a:b; }
inline int Min(int a,int b) { return a>b?b:a; }
const int inf = 0x3f3f3f3f;
const int maxn = 2e3+5;
const int maxk = 2e6+5;

int gcd(int a, int b)
{ return b==0?a:gcd(b,a%b); }
int A, B;
int oula[maxn];
bool g[maxn][maxn];

void init()
{
    memset( g, false, sizeof(g) );
    int i, j;
    for ( i = 0; i < maxn; i++ )
        oula[i] = i;

    for ( i = 2; i < maxn; i++ )
        if ( oula[i] == i )
            for ( j = i; j < maxn; j+=i )
                oula[j] = oula[j]/i*(i-1);

    for( i = 1; i < maxn; i++ )
        for( j = 1; j < maxn; j++ )
            if( gcd(i,j) == 1 )
                g[i][j] = true;
}

int main()
{
    init();
    while ( ~scanf("%d%d", &A, &B)&&A&&B )
    {
        if( A > B ) swap(A,B);    
        double sum = 0;

        for ( int i = 1; i <= A; i++ )
        {
            sum += oula[i]*(B/i);
            int tmp = B%i;
            for( int j = 1; j <= tmp; j++ )
                if ( g[i][j] )
                    sum++;
        }
        
        double ans = sum*2 + 2;
        double all = (unsigned long long)A*B*2+A+B;
        printf( "%.7lf
", ans/all );
    }

    return 0;
}