matlab中else if语句只执行了第二句,程序没问题,逻辑上哪里有错误?

weight=input('the weight of your purse:');
if weight2&&weight=70&&weight100;%weight>100可省略
disp('too heavy to send!');
end
end
end
可以改进一下：
weight=input('the weight of your purse:');
if weight2&&weight=70&&weight100;%%%weight>100;可省略
disp('too heavy to send!');
end
再问： 恩，看来我的错误在于‘2