Go: package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	for scanner.Scan() {
		t, _ := strconv.Atoi(scanner.Text())
		if t == 0 {
			break
		}
		scanner.Scan()
		n, _ := strconv.Atoi(scanner.Text())
		for i  := 0; i < n; i++ {
			scanner.Scan()
			buf := strings.Split(scanner.Text(), " ")
			s, _ := strconv.Atoi(buf[0])
			f, _ := strconv.Atoi(buf[1])
			t -= (f-s)
		}
		if t <= 0 {
			fmt.Println("OK")
		} else {
			fmt.Println(t)
		}
	}
}

C++: #include <iostream>
using namespace std;

int main() {
  int d, n, s, t, sum;
  
  while(cin>>d>>n) {
    for(int i=0; i<n; i++) {
      cin >> s >> t;
      sum += t-s;
    }
    if(sum<d) cout << sum-d << endl;
    else cout << "OK" << endl;
  }
  
  return 0;
}

C++: #include<stdio.h>
int main(){
  int a,n,b,c,sum;
  while(scanf("%d",&a),a!=0){
    scanf("%d",&n);
    sum = 0;
    for(int i=0;i<n;i++){
      scanf("%d %d",&b,&c);
      sum += c-b;
    }
    if(a <= sum) puts("OK");
    else printf("%d\n",a-sum);
  }
  return (0);
}

C++: #include<iostream>
using namespace std;
int main() {
	int n, t, sum = 0, s, f;
	while(cin >> n&&n != 0) { 
		cin >> t;
		for (int i = 0; i < t; i++) {
			cin >> s >> f;
			sum += (f - s);
		}
		if (n <= sum) cout << "OK" << endl;
		else cout << n - sum << endl;
	}
}

C++: #include<iostream>
#include<math.h>
#include<algorithm>
#include<string>
using namespace std;

int t,n,s,f,sum;

int main(){
	while(1){
		sum=0;
		cin>>t;
		if(t==0){break;}
		cin>>n;
		for(int i=0;i<n;i++){
			cin>>s>>f;
			sum+=f-s;
		}
		if(t<=sum){cout<<"OK"<<endl;}
		else{cout<<t-sum<<endl;}
	}
	return 0;
}

C++: #include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

int main() {
	while (true) {
		int t, n, s, f;
		int sum = 0;
		
		cin >> t;
		if (t == 0) break;

		cin >> n;

		for (int i = 0; i < n; i++) {
			cin >> f >> s;
			sum += (f - s);
		}

		if (sum >= t) {
			cout << "OK" << endl;
		} else {
			cout << t - sum << endl;
		}
	}
	return 0;
}

C++: #include<iostream>
using namespace std;

int main(){
	for(int D=0; D<100; D++){
		int t, n, h = 0;
		cin >> t;
		if(t == 0)break;

		else{

			cin >> n;

			for(int i =0; i<n; i++){
				int s, f;
				cin >> s >> f;
				h += (f-s);
			}
			
			if(h >= t){
				cout << "OK" << endl;
			}
			else{
				cout << t-h << endl;
			}

		}
		
	}
	return 0;

}

C++: #include<stdio.h>
int main(void)
{
	int a,b,c[100],d[100],i,n;
	scanf("%d",&a);
	scanf("%d",&b);
	for(i=1;i<=b;i++){
		scanf("%d %d",&c[i],&d[100]);
		if(c[i]<d[i]){
			n+=d[i]-c[i];
		}
		else{
			n+=c[i]-d[i];
		}
	}
	if(a<=n){
		printf("OK\n");
	}
	else{
		n=a-n;
		printf("%d\n",n);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int main() {

    int t, n;
    int s, f;

    while(cin >> t, t) {

        cin >> n;

        int sum = 0;

        for(int i = 0; i < n; ++i) {
            cin >> s >> f;
            sum += f - s;
        }

        if(sum >= t) {
            cout << "OK" << endl;
        } else {
            cout << t - sum << endl;
        }

    }

}

C++: #include <iostream>
using namespace std;

int main(void)
{
	int t,n;
	int a,b;
	int sum;

	while(1)
	{
		cin >> t;
		if(t == 0)
			return 0;

		cin >> n;

		sum = 0;
		for(int i=0;i<n;++i)
		{
			cin >> a >> b;
			sum += b - a;
		}
		if(t <= sum)
			cout << "OK" << endl;
		if(t > sum)
			cout << t - sum << endl;
	}
	return 0;
}

C++: #include <iostream>
using namespace std;

int main() {
	int n,t,s,f,g;
	while (cin >> t && t>0) {
	 cin >> n; g=0;
	 for (;n>0;n--) { cin >> s >> f; g+=f-s;}
	 if (g<t) cout << t-g; else cout << "OK";
	 cout << endl;
 }
 return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int main(){
  int n,i,c,a,b;
  while(cin>>n,n){
    cin>>c;
    int y=0;
    for(i=0;i<c;i++){
      cin>>a>>b;
      y+=b-a;
    }
    if(y>=n)cout<<"OK"<<endl;
    else cout<<n-y<<endl;
  }
}

C++: #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
 
using namespace std;
 
#if __GNUC__
#include <tr1/unordered_map>
#include <tr1/unordered_set>
using namespace tr1;
#else
#include <unordered_map>
#include <unordered_set>
#endif
 
#ifdef __GNUC__
template <class T> int popcount(T n);
template <> int popcount(unsigned int n) { return __builtin_popcount(n); }
template <> int popcount(int n) { return __builtin_popcount(n); }
template <> int popcount(unsigned long long n) { return __builtin_popcountll(n); }
template <> int popcount(long long n) { return __builtin_popcountll(n); }
#else
#define __typeof__ decltype
template <class T> int popcount(T n) { return n ? 1 + popcount(n & (n - 1)) : 0; }
#endif
 
#define rep(i, n) for (int i = 0; i < (int)n; ++i)
#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define rforeach(it, c) for (__typeof__((c).rbegin()) it=(c).rbegin(); it != (c).rend(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define CL(arr, val) memset(arr, val, sizeof(arr))
#define COPY(dest, src) memcpy(dest, src, sizeof(src))
 
template <class T> void max_swap(T& a, const T& b) { a = max(a, b); }
template <class T> void min_swap(T& a, const T& b) { a = min(a, b); }
 
typedef long long ll;
typedef pair<int, int> pint;
 
template <class T, class U> ostream& operator<<(ostream& os, pair<T, U>& p) { os << "( " << p.first << ", " << p.second << " )"; return os;  }
 
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
 
 
const int mod = 1000000007;
const double PI = acos(-1.0);
const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };
bool valid_pos(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }
 
template <class T> void print(T a, int n, int br = 1, const string& deli = ", ") { cout << "{ "; for (int i = 0; i < n; ++i) { cout << a[i]; if (i + 1 != n) cout << deli; } cout << " }"; while (br--) cout << endl; }
template <class T> void print(const vector<T>& v, int br = 1, const string& deli = ", ") { print(v, v.size(), br, deli); }
template <class T> void print2d(T a, int w, int h, int width = -1, int br = 1) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) {	if (width != -1) cout.width(width); cout << a[i][j] << ' ';	} cout << endl; } while (br--) cout << endl; }
 
template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T, class U> void input(T& a, U& b, int n) { for (int i = 0; i < n; ++i) cin >> a[i] >> b[i]; }
 
 
 
int main()
{
	ios::sync_with_stdio(false);

	int t, n, s, e;
	while (cin >> t, t)
	{
		cin >> n;
		int sum = 0;
		while (n--)
			cin >> s >> e, sum += e - s;
		if (sum >= t)
			cout << "OK" << endl;
		else
			cout << t - sum << endl;
	}
}