为何CE

#include <bits/stdc++.h>
using namespace std;
const int N=107,mod=1e9+7;
int la,lb,lc;
int f[N][N][N];
char a[N],b[N],c[N];
string ans[N][N][N];
signed main() {
	//ios::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
	cin>>(a+1)>>(b+1)>>(c+1);
	la=strlen(a+1),lb=strlen(b+1),lc=strlen(c+1);
	for(int i=1;i<=la;++i)
		for(int j=1;j<=lb;++j)
			for(int k=1;k<=lc;++k) {
				if(a[i]==b[j]&&b[j]==c[k])
					if(f[i-1][j-1][k-1]+1>f[i][j][k])
						f[i][j][k]=f[i-1][j-1][k-1]+1,
						ans[i][j][k]=ans[i-1][j-1][k-1]+a[i];
				if(f[i-1][j][k]>f[i][j][k])
					f[i][j][k]=f[i-1][j][k],ans[i][j][k]=ans[i-1][j][k];
				if(f[i][j-1][k]>f[i][j][k])
					f[i][j][k]=f[i][j-1][k],ans[i][j][k]=ans[i][j-1][k];
				if(f[i][j][k-1]>f[i][j][k])
					f[i][j][k]=f[i][j][k-1],ans[i][j][k]=ans[i][j][k-1];
			}
	return 0;
}