string stripSurroundingSpaces(string s) {
		int i = 0;
		while(i<s.size() && s[i] == ' ') {
			i++;
		}
		int j = s.size()-1;
		while(j >= 0 && s[j] == ' ') {
			j--;
		}

		string res;
		for(int k=i; k<=j; ++k)
			res += s[k];
		return res;
	}