Bit string

input/code.cpp: In function 'int32_t main()':
input/code.cpp:33:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.lg;i++){
               ^

#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
#define ll long long
#define pi pair<int,int>
#define pl pair<ll,ll>
#define pd pair<double,double>
#define ld long double
#define pld pair<ld,ld>
#define lg length()
#define sz size()
#define vi vector<int>
#define vl vector<ll>
#define vp vector<pi>
#define vpl vector<pl>
#define pb push_back
#define INF 1000000005
#define LINF 1000000000000000005

string s;

int a,b;

int32_t main(){
	ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
#ifdef LOCAL_DEFINE
	ifstream cin("input.in");
#endif
	
	int t=0;
	cin >> s;
	for(int i=0;i<s.lg;i++){
		if(s[i]=='1') t++;
		if(t%2) a++;
		else b++;
	}
	cout << a*(a-1)/2+b*(b-1)/2+b;
	
#ifdef LOCAL_DEFINE
	cerr << "\nTime elapsed: " << 1.0*clock()/CLOCKS_PER_SEC << " \n";
#endif
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 1

Verdict: ACCEPTED

Test 7

Group: 1

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: WRONG ANSWER

Test 16

Group: 3

Verdict: WRONG ANSWER

Test 17

Group: 3

Verdict: WRONG ANSWER

Test 18

Group: 3

Verdict: WRONG ANSWER

Test 19

Group: 3

Verdict: WRONG ANSWER

Test 20

Group: 3

Verdict: ACCEPTED

Test 21

Group: 3

Verdict: ACCEPTED