Forgotten measurements

input/code.cpp: In function 'int main()':
input/code.cpp:13:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |     for (int i = 0; i < input.size()-3; i++) {
      |                     ~~^~~~~~~~~~~~~~~~

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef uint64_t u64;

int main()
{
    string input;
    cin >> input;
    u64 out = 1;
    u64 i = 0;
    for (int i = 0; i < input.size()-3; i++) {
        if (input[i] == input[i+2] && input[i+1] == input[i+3]) {
            input.erase(i+1, 2);
        }
    }
    while (i < input.size()-2)
    {
        if (input[i] == 'U' && input[i + 2] == 'D')
        {
            out++;
            i += 2;
            //input.erase(i, 4);
            //i = i<2 ? 0 : i-2;
        } else
        if (input[i] == 'D' && input[i + 2] == 'U')
        {
            out++;
            i += 2;
            //input.erase(i, 4);
            //i = i<2 ? 0 : i-2;
        } else
        if (input[i] == 'L' && input[i + 2] == 'R')
        {
            out++;
            i += 2;
            //input.erase(i, 4);
            //i = i<2 ? 0 : i-2;
        } else
        if (input[i] == 'R' && input[i + 2] == 'L')
        {
            out++;
            i += 2;
            //input.erase(i, 4);
            //i = i<2 ? 0 : i-2;
        }
        i++;
    }
    cout << out;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: TIME LIMIT EXCEEDED

Test 10

Verdict: TIME LIMIT EXCEEDED

Test 11

Verdict: TIME LIMIT EXCEEDED