/* Sun Jul  4 02:38:26 JST 2004 */
/* Sun Jul  4 02:53:52 JST 2004 */
#include <stdio.h>

void cut(int x[64], int n, int p, int c)
{
  int i, d[64];
  for (i = 0; i < n; i++) {
    if (0 <= i && i < p-1)   { d[i+c] = x[i]; }
    else if (p-1 <= i && i < c+p-1) { d[i-p+1] = x[i]; }
    else { d[i] = x[i]; }
  }
  for (i = 0; i < n; i++) { x[i] = d[i]; }
}

int main()
{
  int i, n, r, p, c, x[64];
  while (1) {
    scanf("%d%d", &n, &r); if (n == 0 && r == 0) { break; }
    for (i = 0; i < n; i++) { x[i] = n-i; }
    for (i = 0; i < r; i++) {
      scanf("%d%d", &p, &c);
      cut(x, n, p, c);
    }
    printf("%d\n", x[0]);
  }
  return 0;
}