考试的时候0分，现在90分，求调必关

#include<cmath>
#include<bits/stdc++.h>
using namespace std;
int m,n,s,a,b;
struct xx{
	int bh;
	int jg;
}n1[100003];
bool cmp(struct xx x,struct xx y){
	if(x.bh==y.bh)return x.jg<=y.jg;
	return x.bh<y.bh;
}
int main()
{
	cin>>m>>n;
	for(int i=1;i<=n;i++){
		cin>>n1[i].bh>>n1[i].jg;
	}
	sort(n1+1,n1+1+n,cmp);
	s=n1[1].jg;
	a=n1[1].bh;
	for(int i=1;i<=n;i++){
		if(a!=n1[i].bh){
			s=s+n1[i].jg;
			a=n1[i].bh;
			b=b+1;
		}
		if(b==m)break;
	}
	cout<<s;
	return 0;
}