AC：30

TLE：3

WA：9

#include <bits/stdc++.h>
#pragma GCC optimize(1)
#pragma GCC optimize(2)
#pragma GCC optimize(3,"Ofast","inline")
using namespace std;
int main(){
    long long n;
    ios::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
    cin>>n;
    vector<long long>a(n);
    for (int i=0;i<n;i++){
        cin>>a[i];
    }
    vector<pair<long long,long long> >ans;
    for(int j=1;j<n;j++){
    	if(a[j]<a[j-1]){
	       	while(a[j]<a[j-1]){
	            if(a[j]>0||a[j-1]>0){
	        		ans.push_back({j,j+1});
	           		a[j] +=a[j-1];
	        	}
	        	else{
	        		ans.push_back({j+1,j});
	           		a[j-1]+=a[j];
	        	}
	       	}
	    }
    }
    cout<<ans.size()<<endl;
    for(int i=0;i<ans.size();i++){
        cout<<ans[i].first<<" "<<ans[i].second<<endl;
    }
    return 0;
}