#include<iostream>
using namespace std;
struct node{
    int a;
    int b;
}c[101];
bool cmp(node x,node y){
    return x.a < y.a;
}
int main(){
    int m,n,s=0;
    int i,j;
    int sum = 0;
    cin>>m>>n;
    for(i = 0; i < n; i++){
        cin>>c[i].a>>c[i].b;
    }
    sort(c,c+n,cmp);
    for(i = 0; i < n; i++){
        for(j = 1; j <= c[i].b; j++){
            sum += c[i].a;
            if(sum>=m){
            	break;
        	}
        	s++;
        }      
    }    
    cout<<s;
    return 0;
}

```#include <bits/stdc++.h> 
using namespace std;
int main() {
    int m, n;
    cin >> m >> n;
    vector<int> dp(m + 1, -1);  
    dp[0] = 0;  
    
    for (int i = 0; i < n; ++i) {
        int a, b;
        cin >> a >> b;  
        for (int w = m; w >= 0; --w) {  
            if (dp[w] != -1) {

                for (int k = 1; k <= b; ++k) {
                    int new_w = w + a * k;
                    if (new_w > m) break;  
                    if (dp[new_w] < dp[w] + k) {
                        dp[new_w] = dp[w] + k;
                    }
                }
            }
        }
    }
    
    int max=0;
    for (int w=0;w<=m;++w) {  
        if (dp[w]>max) {
            max = dp[w];
        }
    }
    
    cout<<max<<endl;  
    
    return 0;
}