#include <stdio.h>
#include <iostream>
using namespace std;

void oneProblem(){
	int nums=0;
	scanf("%d",&nums);	
//cout<<nums<<endl;
	int *arr=new int[nums];
	int *res=new int[nums];
	int *tah=new int[nums];
 for(int i=0;i<nums;++i){
		scanf("%d",&arr[i]);
		scanf("%d",&res[i]);
		//res[i]=a;
		tah[i]=0;
		//cout<<res[i]<<"/"<<arr[i]<<endl;
		res[i]++;
	}
	int b=1;
	while(true){
				
		for(int i=0;i<nums;++i){
				if(tah[i]>=b)
					continue;
				if(i){
					if(arr[i-1]<arr[i]-1){
						arr[i-1]=arr[i];
						tah[i-1]=tah[i]+1;		
					}
				}
				if(i!=nums-1){
					if(arr[i+1]<arr[i]-1){
						arr[i+1]=arr[i];
						tah[i+1]=tah[i]+1;		
					}
				}
				tah[i]++;//++tah
				arr[i]++;//posun doprava
				//cout<<i<<":"<<arr[i]<<"/"<<tah[i]<<"/"<<res[i]<<endl;
		}//cout<<"----"<<endl;
		for(int i=0;i<nums;++i){
				if(arr[i]>=res[i]){
					//cout<<i<<endl;
					printf("K prechodu reky je treba %d pontonu.\n",(tah[i]-1));	
					goto AAA;
				}

		}		
		++b;
	}	
	AAA:
	delete[]tah;
	delete[]res;
	delete[]arr;
}

int main(void){
	int DW;
	scanf("%d",&DW);
	for(int AmyPond=0;AmyPond<DW;++AmyPond)
		oneProblem();	

	return 0;
}