B. Alyona and flowers

#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<int>v;
    int n,m,x,ini,fin,resp=0;
    cin>>n>>m;
    for (int i=0;i<n;i++){
        cin>>x;
        v.push_back(x);
    }
    for (int i=0;i<m;i++){
        cin>>ini>>fin;
        int aux=0;
        for (int j=ini-1;j<fin;j++){
            aux+=v[j];
        }
        if (aux>0)
            resp+=aux;
    }
    cout<<resp<<endl;

    return 0;
}