/*********integra con metodo dei trapezi********/
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv){
    FILE *f;
    double sum,x1,x2,y1,y2,a;
    int N,i;
      f=fopen(argv[1],"r");
    if (f==NULL){
	fprintf(stderr,"error in imput: insert nomefile\n");
	exit(0);
    }
    N=0;
    while (fscanf(f,"%lf %lf",&x1,&y1)!=EOF){
	N++;
    }
    rewind(f);
    sum=0.;
    fscanf(f,"%lf %lf",&x1,&y1);
    for(i=0;i<N-1;i++){
	fscanf(f,"%lf %lf",&x2,&y2);
	sum+=(y1+y2)*(x2-x1)*0.5;
	x1=x2;
	y1=y2;
fprintf(stdout,"%lf %lf\n",x1,sum);
    }
  return 0;
}