我尝试在Ubuntu 17.04上安装npm时出错

I'm trying to install npm on Ubuntu 17.04 but I'm not getting it. I've installed nodejs and nodejs-legacy and when I try to install npm, a message appears saying that npm depends on node-gyp (>= 0.10.9) and won't be installed. If a try to install node-gyp, another dependency appears and successively. Does anybody know how to fix it?I'm trying to install npm on Ubuntu 17.04 but I