#include<stdio.h>

int main(void){
  int i;
  int N, H, M, h, m;
  int t = 0;
  scanf("%d", &N);
  for(i = 0; i < N; i++){
    scanf("%d:%d %d:%d", &H, &M, &h, &m);
    printf("H = %d\n", H);
    printf("M = %d\n", M);
    printf("h = %d\n", h);
    printf("m = %d\n", m);
    if(H > h)t += (24 - H) * 60 - M;
    else t -= H * 60 + M;
    t += h * 60 + m;
    printf("t = %d\n", t);
  }
  printf("%d\n", t);
  return 0;
}