I am 26 year old.my hight is 172cm.my weight is 57.but for my height I have to b 72.so I want to gain weight.so... give me tips:)

First of all, don't be so anxious to gain weight unless your low weight is causing health problems. Your height and weight are actually very close to my own. Everyone's body is a little different, and "ideal weight" is only a general guideline to consider if you are grossly deviating from it.

The most healthy way to put on weight is to put on muscle. Believe it or not, for those who are not overweight, exercise can help you gain weight. Eat right (for weight gain, up your protein, water, and vegetable intake while reducing fat unless you already eat low fat) and daily exercise is the best advise I can give. Weight training will do better to put on bulk. Take a daily multivitamin to make sure that you are not missing anything essential.

Finally, unless there is some reason that you NEED to put on this weight, I would advise against it as a goal. There's nothing wrong with diet and exercise causing some weight gain from muscle mass, but you don't sound like you are in need of the weight for health reasons.

Not what I wanted to know