Add a natural number N to the numerator and denominator of (17/49), and the ratio of the numerator to the denominator of the new fraction obtained is 1:2. What is the natural number N=?
把(17/49)的分子和分母同时加上一个自然数N，所得的新分数的分子与分母的比是1：2．自然数N=多少．
<result>15</result>