P1439

#include<bits/stdc++.h>

using namespace std;

const int N=1005;

int c,n;
int w[N],v[N];
int dp[N][N];

int main(){
    while(scanf("%d%d",&c,&n)!=EOF){
        memset(dp,0,sizeof(dp));
        for(int i=1;i<=n;i++){
            cin>>w[i]>>v[i];
        }
        for(int i=1;i<=n;i++){
            for(int j=1;j<=c;j++){
                if(j<w[i]){
                    dp[i][j]=dp[i-1][j];
                }else{
                    dp[i][j]=max(dp[i-1][j],dp[i-1][j-w[i]]+v[i]);
                }
            }
        }
        cout<<dp[n][c]<<endl;
    }
    return 0;
}