http://projecteuler.net/problem=27 [Answer:-59231]

#include <iostream>#include <cmath>using namespace std;bool IsPrime( int m ){    if ( m < 2 )    {        return false;    }    int d = sqrt( m + 0.5 );    for ( int i = 2; i <= d; ++i )    {        if ( m % i == 0 )        {            return false;        }    }    return true;}int main(){    int max_n = 0;    int result;    for ( int a = -1000; a <= 1000; ++a )    {        for ( int b = -1000; b <= 1000; ++b )        {            int n = 0;            while ( IsPrime( (n + a) * n + b ) )            {                ++n;            }            if ( n > max_n )            {                result = a * b;                max_n = n;            }        }    }    cout << result << endl;    return 0;}