#include <stdio.h>
int main(){
int n,i,t=0;
char s[10001];
scanf("%d%d",&n,&n);i=n-1;
scanf("%s",s);n=s[i];
while(t-81+n*2)t+=s[n-40?--i:++i]*2-81;
printf("%d\n",i+1);
return 0;
}