#include "stdio.h"

#include "stdlib.h"

#include "string.h"

#define maxn 1000000

#define GREEN 'G'

#define RED 'R'

#define NOT_A_LOC 0xffffffff

int loc[2 * maxn + 2];

int sum[maxn + 1];

char a[maxn + 1];

int hash(int index) { return index + maxn; }

int max(int a, int b) { return a > b ? a : b; }

int main() {

scanf("%s", a + 1);

int n = strlen(a + 1);

int res = 0;

memset(loc, NOT_A_LOC, sizeof(loc));

loc[hash(0)] = 0;

for (int i = 1; i <= n; i++) {

if (i) sum[i] = sum[i - 1];

if (a[i] == GREEN) sum[i] += 1;

else sum[i] -= 1;

if (loc[hash(sum[i])] != NOT_A_LOC) {

res = max(res, i - loc[hash(sum[i])]);

}

else loc[hash(sum[i])] = i;

}

printf("%d", res);

return 0;

}