#include<bits/stdc++.h>
using namespace std;
template<typename T> inline void read(T &x){
	x=0;bool f=0;char c=getchar();
	for(;c<'0'||c>'9';c=getchar())f|=(c=='-');
	for(;c>='0'&&c<='9';c=getchar())x=x*(T)10+c-'0';
	x=f?-x:x;
}
int n,q;
bool a[200005];
int sum[200005];
int mn[200005],Mn[200005];
int mx[200005],Mx[200005];
int main(){
	int T;
	for(read(T);T--;){
		read(n),read(q);
		mn[0]=mn[n+1]=Mn[0]=Mn[n+1]=0;
		mx[0]=mx[n+1]=Mx[0]=Mx[n+1]=0;
		for(int i=1;i<=n;i++)a[i]=(getchar()=='-')?0:1,sum[i]=sum[i-1]+(a[i]?1:-1);
		for(int i=1;i<=n;i++)mn[i]=min(mn[i-1],sum[i-1]+(a[i]?1:-1));
		for(int i=n;i>=1;i--)Mn[i]=min(0,Mn[i+1]+(a[i]?1:-1));
		for(int i=1;i<=n;i++)mx[i]=max(mx[i-1],sum[i-1]+(a[i]?1:-1));
		for(int i=n;i>=1;i--)Mx[i]=max(0,Mx[i+1]+(a[i]?1:-1));
		for(int l,r;q--;){
			read(l),read(r);
			int Max=mx[l-1],Min=mn[l-1];
			Max=max(Max,sum[l-1]+Mx[r+1]);
			Min=min(Min,sum[l-1]+Mn[r+1]);
			printf("%d\n", 1+Max-Min);
		}
	}
	return 0;
}
