用cin输入简单一点，用scanf代码短一点

#include<cstdio>
int main()
{
    double a,b,c;
    scanf("%lf %lf %lf",&a,&b,&c);
    if(a+b>c&&a+c>b&&b+c>a)
    printf("Perimetro = %.1lf",a+b+c);
    else
    printf("Area = %.1lf",(a+b)*c/2);
    return 0;
}