Submission #71348258

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#include <stdio.h>
#define MOD_BY 1000000007
int add(int a, int b) {
  return a + b - MOD_BY * (a + b >= MOD_BY);
}
int N;
char s[4096];
int memo[4096][4096];
int calc(int pos, int available) {
  int unavailable = N - pos - available; /* この要素の候補ではない要素の数を計算する */
  int ans = 0;
  int i;
  if (pos >= N) return 1;
  if (memo[pos][available]) return ~memo[pos][available];
  for (i = 0; i < available; i++) {
    int next_available;
 
 
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#include <stdio.h>

#define MOD_BY 1000000007

int add(int a, int b) {
	return a + b - MOD_BY * (a + b >= MOD_BY);
}

int N;
char s[4096];

int memo[4096][4096];

int calc(int pos, int available) {
	int unavailable = N - pos - available; /* この要素の候補ではない要素の数を計算する */
	int ans = 0;
	int i;
	if (pos >= N) return 1;
	if (memo[pos][available]) return ~memo[pos][available];
	for (i = 0; i < available; i++) {
		int next_available;
		if ((pos == 0 ? '<' : s[pos - 1]) == s[pos]) {
			/* 同じ方向 → 今の所より「上」のみを次に使える */
			next_available = available - i - 1;
		} else {
			/* 違う方向 → 今の所より「下」のみを次に使える */
			next_available = unavailable + i;
		}
		ans = add(ans, calc(pos + 1, next_available));
	}
	return ~(memo[pos][available] = ~ans);
}

int main(void) {
	if (scanf("%d", &N) != 1) return 1;
	if (scanf("%4095s", s) != 1) return 1;
	printf("%d\n", calc(0, N));
	return 0;
}

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