#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];
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];
double ans = 0;
for(int i = 0,xa,xb;i < m;++i){
scanf("%d %d",&xa,&xb);
--xa; --xb;
double aux = 0,mn = F[xa];
for(int j = xa;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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