**区间和的C语言版本**

#include <stdio.h>
#include <stdlib.h>

#define N 300010

typedef struct{
    int first;
    int second;
}PII;

int a[N],s[N];
int alls[N];
PII add[N];
PII query[N];

void quick_sort(int alls[],int l,int r){
    if(l>=r) return;

    int i=l-1,j=r+1,x=alls[(r+l)/2];

    while(i<j){
        do i++; while(alls[i]<x);
        do j--; while(alls[j]>x);
        if(i<j){
            int temp=alls[i];
            alls[i]=alls[j];
            alls[j]=temp;
        }
    }

    quick_sort(alls,l,j);
    quick_sort(alls,j+1,r);
}

int unique(int alls[],int len){
    int* end=alls+len;
    int* result_end=alls+1;
    for(int* p=alls+1;p<end;p++){
        if(*p!=*(p-1)){
            *result_end=*p;
            result_end++;
        }
    }

    return result_end-alls;
}

int find(int x,int size){
    int l=0,r=size-1;
    while(l<r){
        int mid=(l+r)/2;
        if(alls[mid]<x) l=mid+1;
        else r=mid;
    }

    return r+1;
}

int main(){
    int n,m;
    scanf("%d %d",&n,&m);

    int add_count=0,query_count=0,alls_count=0;

    for(int i=0;i<n;i++){
        int x,c;
        scanf("%d %d",&x,&c);
        add[add_count++]=(PII){x,c};
        alls[alls_count++]=x;
    }

    for(int i=0;i<m;i++){
        int l,r;
        scanf("%d %d",&l,&r);
        query[query_count++]=(PII){l,r};
        alls[alls_count++]=l;
        alls[alls_count++]=r;
    }

    quick_sort(alls,0,alls_count-1);
    alls_count=unique(alls,alls_count);

    for(int i=0;i<alls_count;i++){
        int x=find(add[i].first,alls_count);
        a[x]+=add[i].second;
    }

    for(int i=1;i<=alls_count;i++){
        s[i]=s[i-1]+a[i];
    }

    for(int i=0;i<query_count;i++){
        int l=find(query[i].first,alls_count);
        int r=find(query[i].second,alls_count);
        printf("%d\n",s[r]-s[l-1]);
    }

    return 0;
}