A Sweet Journey

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 0 Accepted Submission(s): 0

Problem Description
Master Di plans to take his girlfriend for a travel by bike. Their journey, which can be seen as a line segment of length L, is a road of swamps and flats. In the swamp, it takes A point strengths per meter for Master Di to ride; In the flats, Master Di will regain B point strengths per meter when riding. Master Di wonders：In the beginning, he needs to prepare how much minimum strengths. (Except riding all the time,Master Di has no other choice)

Input
In the first line there is an integer t (1≤t≤50), indicating the number of test cases.
For each test case:
The first line contains four integers, n, A, B, L.
Next n lines, each line contains two integers: Li,Ri, which represents the interval [Li,Ri] is swamp.
1≤n≤100,1≤L≤105,1≤A≤10,1≤B≤10，1≤Li

#include<stdio.h>int main(){    int ans=0,num=0,t,A,i,B,j,L,n,arr[101][101],power[101],use[101];    scanf("%d",&t);    while(t)    {        scanf("%d%d%d%d",&n,&A,&B,&L);        for(i=0;i<n;i++)            for(j=0;j<2;j++)            {                scanf("%d",&arr[i][j]);                if(j==1)                {                    use[i]=arr[i][j]-arr[i][j-1];                }                if(i==0)                    power[0]=arr[0][0];                if(i!=0)                    power[i]=arr[i][0]-arr[i-1][1];            }        for(i=0;i<n;i++)        {            num=num+power[i];            num=num-use[i];            if(num<0)            {                ans=ans-num;                num=0;            }        }        printf("%d    ",ans);        t--;    }    return 0;}