#include <stdio.h>

int main(){
    int n,k,i,t=0,m=-1;
    char s[10004];
    
    scanf("%d%d",&n,&k);
    scanf("%s",&s);
    
    if (s[k-1]=='('){
        for (i=0;i<n;i++){
            if (k-1==i) m=t;
            t+=s[i]=='('?1:-1;
            if ((m+1)&&t==m){printf("%d",i+1);exit(0);}
        }
    }else{
        for (i=n-1;i>=0;i--){
            if (k-1==i) m=t;
            t+=s[i]==')'?1:-1;
            if ((m+1)&&t==m){printf("%d",i+1);exit(0);}
        }
    }
    return 0;
}