usaco-practice/cses/Repetitions/index.cpp

#include <iostream>
#include <vector>
using namespace std;

int main() {
  string s;
  cin >> s;
  int ans = 0, c = 0;

  char l = 'A';
  for (char d : s) {
    if (d == l) {
      ++c;
      ans = max(c, ans);
    } else {
      l = d;
      c = 1;
    }
  }

  cout << ans;
}