Some task

#include <stdio.h>

const long max = 100;

bool t;
long i,j,p1,p2,ma;
long n[max];
long a[max][max],b[max][max];


int main()
{

  i = 0;
  while ((scanf("%li\n",&n[i])) == 1) {

    for (j=0;j<n[i];j++) {

    scanf("%li %li\n",&a[i][j],&b[i][j]);

    if (b[i][j] == 0) {
        b[i][j] = a[i][j];
      }

     }

  i += 1;
  }

  ma = i;

  for (i = 0;i<ma;i++) {

    t = true;
    p1 = a[i][0];
    p2 = b[i][0];

    for (j=0;j<n[i];j++) {

        if (a[i][j]>=p1 and b[i][j]<=p2) {

            p1 = a[i][j];
            p2 = b[i][j];

          }
          else
            if (a[i][j]<=p1 and b[i][j]>=p2) {

            p1 = p1;
            p2 = p2;

          }
        else
            if (a[i][j]<=p1 and b[i][j]<=p2 and b[i][j]>=p1) {

            p1 = p1;
            p2 = b[i][j];

          }
        else
            if (a[i][j]>=p1 and b[i][j]>=p2 and p2>=a[i][j]) {

            p1 = a[i][j];
            p2 = p2;

          }
          else
          {
          t = false;
          break;
          }

      }

    if (t == true) {
        printf("YES\n");
      }
      else
        printf("NO\n");
  }

    return 0;
}