#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define eps 1e-8
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f
int n,m,p;
int d[100005];
int a[50005];
ll f[50005][2];
int st[50005];
ll sum[50005];
ll X[50005],Y[50005];
bool checkconvex(int x,int y,int z){
	// (Y[x]-Y[y])/(X[x]-X[y])>=(Y[y]-Y[z])/(X[y]-X[z])
	return (Y[x]-Y[y])*(X[y]-X[z])>=(Y[y]-Y[z])*(X[x]-X[y]);
}
bool checkslope(int x,int y,int k){
	// (Y[x]-Y[y])/(X[x]-X[y])<=k
	// printf("%d %d %d\n",x,y,k);
	// printf("%lld %lld %lld\n",Y[y]-Y[x],k,X[y]-X[x]);
	return (Y[y]-Y[x])<=k*(X[y]-X[x]);
}
int main(){
	scanf("%d%d%d",&n,&m,&p);
	for(int i=2;i<=n;i++)scanf("%d",&d[i]);
	for(int i=2;i<=n;i++)d[i]+=d[i-1];
	for(int i=1;i<=m;i++){
		int h,t;
		scanf("%d%d",&h,&t);
		a[i]=t-d[h];
	}
	sort(a+1,a+m+1);
	// for(int i=1;i<=m;i++)printf("%d %d\n",1027,a[i]);
	for(int i=1;i<=m;i++)sum[i]=sum[i-1]+a[i];
	f[0][0]=0;
	for(int i=1;i<=m;i++)f[i][0]=1e13;
	for(int j=1;j<=p;j++){
		for(int i=0;i<=m;i++){
			X[i]=i;
			Y[i]=f[i][1^(j&1)]+sum[i];
		}
		// printf("j=%d\n",j);
		// if(j>=2)return 0;
		int bk=1,top=0;
		for(int i=1;i<=m;i++){
			while(top>bk && checkconvex(st[top-1],st[top],i-1))--top;
			st[++top]=i-1;
			while(bk<top && checkslope(st[bk],st[bk+1],a[i]))++bk;
			f[i][j&1]=f[st[bk]][1^(j&1)]+(ll)(i-st[bk])*a[i]-(sum[i]-sum[st[bk]]);
			// printf("%d %d\n",bk,st[bk]);
			// printf("f[%d][%d]=%lld\n",i,j,f[i][j&1]);
		}
	}
	printf("%lld",f[m][p&1]);
	return 0;
}
// quod erat demonstrandum