62分求调！

#include<bits/stdc++.h> 
using namespace std;
int a[1005]={0},x,y,price=0,dj,maxm;
int main(){
	cin>>x>>y;
	for(int i=0;i<=y;i++){
		cin>>dj>>maxm;
		a[dj]=a[dj]+maxm;
	} 
	for(int i=0;i<=1000;i++){
		if(x>a[i]){
			x-=a[i];
			price==price+a[i]*i;
		}else if(x>0){
			price+=x*i;
			x=0;
		}else if(x=0){
		    break;
		}
	} 
	cout<<price;
	return 0;
}