http://projecteuler.net/problem=13 [Answer:5537376230]

 #include <cstdio>

using namespace std;

int main()
{
    double sum = 0.0;
    double x;
    while ( scanf("%lf", &x) != EOF )
    {
        sum += x;
    }
    printf("%.10e\n", sum);
    return 0;
}