upgraded triangle in c

#include<stdio.h>
#include<stdlib.h>
#include <math.h>
int calculate(double a,double b, double c, double* p, double* s){
    if(a <= 0 || b<=0 || c<=0){
        return -1;
    }
    *p =  a+b+c;
    double sp = *p / 2;
    *s = sqrt(sp *(sp -a)*(sp -b)*(sp - c));
return 0;
}
int main(){
double a, b,c, p, s;
printf("Enter sides: ");
scanf("%lf %lf %lf", &a, &b, &c);
if(calculate(a,b,c,&p,&s) == -1){
fprintf(stderr, "Invalid sides\n");
return 1;
}
printf("%.2lf\n",p);
printf("%.2lf",s);

return 0;
}