CF1221D Make The Fence Great Again

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<map> 
#include<vector> 
using namespace std;
typedef  long long ll;
const int mod=1e9+7;
const int N=5e5+10;
const ll inf=1e18+10;
ll a[N],b[N];
ll f[N][3];//前i位当前位置修改几次 
int main(){
    int t;
    scanf("%d",&t);
    while(t--){
        int n;
        scanf("%d",&n);
        int i;
        for(i=1;i<=n;i++){
            scanf("%lld%lld",&a[i],&b[i]);
        }
        for(i=0;i<=n;i++){
            for(int j=0;j<3;j++)
            f[i][j]=inf;
        }
        f[0][0]=0;
        int j,k;
        for(i=1;i<=n;i++){
            for(k=0;k<3;k++){
                for(j=0;j<3;j++){
                    if(a[i-1]+j!=a[i]+k){
                        f[i][k]=min(f[i-1][j]+k*b[i],f[i][k]);
                    }
                }
            }
        }
        printf("%lld\n",min(min(f[n][0],f[n][1]),f[n][2]));
    }
}