#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
using namespace std;
double F[150000],P[150000];
double Fmn[150000],Fmx[150000],Fans[150000];
int p[150000];
int main(){
int n,m,C;
scanf("%d %d %d",&n,&m,&C);
int x[n];
for(int i = 0;i < n;++i) scanf("%d",&x[i]);
for(int i = 1;i < n;++i) scanf("%d",&p[i]);
P[0] = 0;
for(int i = 1;i < n;++i)
P[i] = P[i - 1] + p[i] / 100.0;
for(int i = 0;i < n;++i)
F[i] = x[i] / 2.0 - C * P[i];
int sz = (int)floor(sqrt(n));
for(int i = 0;sz*i < n;i++){
Fmn[i] = F[sz*i];
Fmx[i] = F[sz*i];
Fans[i] = 0;
double mn = F[sz*i];
for(int j = 0;j < sz && sz*i + j < n;++j){
Fmn[i] = min(Fmn[i],F[sz*i + j]);
Fmx[i] = max(Fmx[i],F[sz*i + j]);
mn = min(mn,F[sz*i + j]);
Fans[i] = max(Fans[i],F[sz*i + j] - mn);
}
}
double ans = 0;
for(int i = 0,xa,xb;i < m;++i){
scanf("%d %d",&xa,&xb);
--xa; --xb;
double aux = 0;
int l = (xa + sz - 1) / sz,r = xb / sz;
for(int j = l;j < r;++j)
aux = max(aux,Fans[j]);
int x1 = sz * l;
double mn = F[xa];
for(int j = xa;j < x1;++j){
mn = min(mn,F[j]);
aux = max(aux,F[j] - mn);
}
for(int j = l;j < r;++j){
aux = max(aux,Fmx[j] - mn);
mn = min(mn,Fmn[j]);
}
int x2 = sz * r;
for(int j = x2;j <= xb;++j){
mn = min(mn,F[j]);
aux = max(aux,F[j] - mn);
}
ans += aux;
}
printf("%.8f\n",ans);
return 0;
}
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