#include <iostream>

using namespace std;

#define NCARD_MAX 50

int ncard;
int CARD[NCARD_MAX+1];

void operate( int p, int c ) {
  int NEW[NCARD_MAX+1];

  int cursor = 1;
  for ( int i = 0; i < c; i++ )
    NEW[cursor++] = CARD[p+i];

  for ( int i = 1; i < p; i++ )
    NEW[cursor++] = CARD[i];

  for ( int i = p+c; i <= ncard; i++ )
    NEW[cursor++] = CARD[i];

  for ( int i = 1; i <= ncard; i++ )
    CARD[i] = NEW[i];
}

int main() {
  int noperation;

  while ( true ) {
    cin >> ncard >> noperation;
    if ( ncard == 0 && noperation == 0 ) break;

    for ( int c = 1; c <= ncard; c++ ) CARD[c] = ncard-c+1;

    for ( int i = 0; i < noperation; i++ ) {
      int p, c; cin >> p >> c;
      operate(p, c);
    }

    cout << CARD[1] << endl;
  }

  return 0;
}