1-3

#include <stdio.h>

int main()
{
    double arr[21];
    for (int i = 0; i < 21; ++i) {
        scanf("%lf", &arr[i]);
    }

    double sum = 0;
    for (int i = 0; i < 21; ++i) {
        if (arr[i] > 0) {
            sum += arr[i];
        }
    }

    printf("%lf", sum);

    return 0;
}