n = int(input())
s = input()
ct0, ct1 = 0, 0
for i in range(len(s)):
if s[i] == '0':
ct0 += 1
else:
ct1 += 1
print(abs(ct0-ct1))#include<bits/stdc++.h>
using namespace std;
void solvio(){
int n;
cin >> n;
string s;
cin >> s;
int one=0, zero=0;
for(int i=0; i<s.size(); i++){
if(s[i] == '0')zero++;
else one++;
}
int mini = min(one, zero);
cout << n-(2*mini) << endl;
}
int main(){
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
solvio();
return 0;
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